Riley-Clued Crossword

Question

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Below is an ascii version of the image above, for those who cannot view images. All words are 8 characters long.

····················
···············1····
·2·········1_______·
·_········3····_····
·_····4·2_______·5··
·_····_···_····_·_··
·3_______·4_______··
·_····_···_····_·_··
·_·6·5__7___8··_·_··
·_·_··_·_·_·_····_··
···_··_·_·_·_····_··
···_··_·_···_·9··_··
···_···6_______·····
···_····_···_·_·····
···_····_···_·_·····
·7_______···_·_·····
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··············_·····
········8_______····
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Across

1
My first was a delicacy long ago.
My middle improves our quality of life.
My last can be divided or doubled.
Together, I'm in some of the healthiest foods.

2
My first is a protective action. [British]
My middle is the object of learning.
My last meant lunge, long ago.
Together, I'm an herb fed to animals.

3
My first is used for steering.
My middle is just knowledge.
My last is as expected, when true to itself.
Together, parents do this to their young children.

4
My first can come from a well.
My middle describes a well.
My last is smaller.
Together, I'm unresponsive to your screams.

5
My first is a light collector.
My middle is rounded, tight, and thick.
My last is what you do to rubber.
Together, I'm a plant sickness.

6
My first makes things easy to talk about.
My middle is the earth's military haircut.
My last is popular, and made from grass seed.
Together, don't confuse me with another.

7
My first takes care of you, if good.
My middle is a dateless partier.
My last is done by a vintner.
Together, we're an unwilling group.

8
My first describes the candy no one ate.
My middle is The Great Prince of the Forest.
My last describes a seasoned veteran.
Together, I'm something we did to the play.

---

Down

1
My first converts a photo to binary.
My middle is a forced payment, when possible.
My last is weak at 2 lb., but strong at 30+ lb.
Together, I'm more deficient than anyone else.

2
My first can be a portal to another world.
My middle is slimy and tasty.
My last is on a buck.
Together, I'm a primitive database.

3
My first can be under, caught, or fed.
My middle is a second chance, for example.
My last helps you walk.
Together, we facilitate oxygen transfer.

4
My first is often followed by the word up.
My middle has nothing to hide.
My last are sometimes split or loose.
Together, I lean a certain direction.

5
My first is a friend to salt and water.
My middle is bad when it's in the back.
My last can get the job done, for sure.
Together, moisture weakens me.

6
My first is large in many different ways.
My middle is a very giving sequence.
My last is a wet point.
Together, I'm in a tremendous state.

7
My first can be opened, played with, and held.
My middle can be brought up and sat on.
My last are narrow annexes.
Together, we override strength.

8
My first is one of Santa's creations.
My middle usually hurts its object.
My last sounds like a dangerous animal.
Together, I describe food items you ran out of.

9
My first is constructed with a mouth.
My middle is anyone's guess.
My last was murdered (maybe out of jealousy).
Together, I can be put in a subgroup.

Answer 1

I believe this crossword should fully resolve like so:

Some of these words are very obscure, and some of the affixes are a little strangely clued, perhaps, so here are some explanations to help make sense of it all:

Across clues:

1A:
My first was a delicacy long ago. CATE
My middle improves our quality of life. TECH
My last can be divided or doubled. CHIN
Together, I'm in some of the healthiest foods. CATECHIN = CATE+TECH+CHIN (found in tea and pomes)

2A:
My first is a protective action. [British] SAIN (making the sign of the cross)
My middle is the object of learning. INFO
My last meant lunge, long ago. FOIN
Together, I'm an herb fed to animals. SAINFOIN = SAIN+INFO+FOIN (often feed for horses)

3A:
My first is used for steering. REIN
My middle is just knowledge. INFO
My last is as expected, when true to itself. FORM ('true to form')
Together, parents do this to their young children. REINFORM = REIN+INFO+FORM

4A:
My first can come from a well. ECHO
My middle describes a well. HOLE
My last is smaller. LESS
Together, I'm unresponsive to your screams. ECHOLESS = ECHO+HOLE+LESS

5A:
My first is a light collector. LEAF
My middle is rounded, tight, and thick. AFRO
My last is what you do to rubber. ROLL (as a tyre)
Together, I'm a plant sickness. LEAFROLL = LEAF+AFRO+ROLL

6A:
My first makes things easy to talk about. NAME
My middle is the earth's military haircut. MESA (flat top, steep sides)
My last is popular, and made from grass seed. SAKE (the Japanese rice wine)
Together, don't confuse me with another. NAMESAKE = NAME+MESA+SAKE

7A:
My first takes care of you, if good. HOST
My middle is a dateless partier. STAG (as in 'stag do')
My last is done by a vintner. AGES (as in 'the act of aging wine')
Together, we're an unwilling group. HOSTAGES = HOST+STAG+AGES

8A:
My first describes the candy no one ate. REST
My middle is The Great Prince of the Forest. STAG
My last describes a seasoned veteran. AGED
Together, I'm something we did to the play. RESTAGED = REST+STAG+AGED

Down clues:

1D:
My first converts a photo to binary. = SCAN
My middle is a forced payment, when possible. = ANTE (as in a game of poker)
My last is weak at 2 lb., but strong at 30+ lb. TEST (strength of a fishing line)
Together, I'm more deficient than anyone else. SCANTEST = SCAN+ANTE+TEST

2D:
My first can be a portal to another world. BOOK (metaphorically) (books are great)
My middle is slimy and tasty. OKRA
My last is on a buck. RACK (another word for antlers)
Together, I'm a primitive database. BOOKRACK = BOOK+OKRA+RACK (a categorised store of information!)

3D:
My first can be under, caught, or fed. FIRE ('under fire', 'catch fire', 'feed the fire')
My middle is a second chance, for example. REDO
My last helps you walk. DOGS (US slang for 'feet' - definition 6 in the link)
Together, we facilitate oxygen transfer. FIREDOGS = FIRE+REDO+DOGS (part of a fire surround, raising burning logs to improve oxygen flow during the burning process)

4D:
My first is often followed by the word up. PROP ('prop up')
My middle has nothing to hide. OPEN (honest, revealing)
My last are sometimes split or loose. ENDS ('split ends', 'loose ends')
Together, I lean a certain direction. PROPENDS = PROP+OPEN+ENDS

5D:
My first is a friend to salt and water. RUST
My middle is bad when it's in the back. STAB
My last can get the job done, for sure. ABLE
Together, moisture weakens me. RUSTABLE = RUST+STAB+ABLE

6D:
My first is large in many different ways. HUGE
My middle is a very giving sequence. GENE (a sequence of DNA bases, 'giving' their properties to the next generation)
My last is a wet point. NESS
Together, I'm in a tremendous state. HUGENESS = HUGE+GENE+NESS

7D:
My first can be opened, played with, and held. FIRE
My middle can be brought up and sat on. REAR ('bring up the rear', part of the body to sit upon)
My last are narrow annexes. ARMS
Together, we override strength. FIREARMS = FIRE+REAR+ARMS

8D:
My first is one of Santa's creations. LIST
My middle usually hurts its object. STAB
My last sounds like a dangerous animal. ABLE ("a bull")
Together, I describe food items you ran out of. LISTABLE = LIST+STAB+ABLE (put them on the shopping list!)

9D:
My first is constructed with a mouth. NEST (built by birds using their beaks)
My middle is anyone's guess. STAB ('a stab in the dark')
My last was murdered (maybe out of jealousy). ABEL ("ABEL", murdered by his brother Cain in Genesis)
Together, I can be put in a subgroup. NESTABLE = NEST+STAB+ABLE

Of note is that many affixes reappear across different words using different clues. I suspect this is just a self-imposed constraint by the OP during construction of the puzzle, and doesn't conceal any further steps that require solving.