Across
5. a joke of grand scale
6. drugged sea
7. very friendly walker
10. give parts of songs
Down
1. sneaky carrier
2. most difficult dislike
3. violent injury of highest form
4. thin expensive ore pieces
9. hot surface for people's opinions

• Just noticed I missed one box on 2 down. it should be one longer. my apologies. ill edit in a correct grid – Dragonrage Mar 27 '18 at 22:03

All the clues are

in two parts, one defining the answer and the other defining an anagram of the answer.

So the solution is, with help from gnovice and Aces:

- in the order in which they appear in the clue
- asterisked answer is the one that goes in the grid
- if no asterisk, then either answer can go in the grid

Across

5. COMICS* / COSMIC (thanks to gnovice)
6. COCAINE / OCEANIC*
7. CHARMER / MARCHER* (thanks to Aces)
8. SERPENT / PRESENT*
10. SERVE / VERSE

Down

1. COVERT / VECTOR* (thanks to gnovice)
2. HARDEST / HATREDS (thanks to gnovice)
3. MUTILATE / ULTIMATE (thanks to gnovice)
4. SLIVERS* / SILVERS

Commentary:

Not a bad puzzle, but it would be improved if
a) there was a unique solution; and
b) the clues agreed in tense, case and number with the answers. "parts of songs" is VERSES, not VERSE; COCAINE is a drug, not drugged, and so on.

• see my edit. sorry for the trouble – Dragonrage Mar 27 '18 at 22:07
• Thanks for the comments, I'll keep those in mind. Hope it was enjoyable at least. Was a little surprised you caught the trick so quickly. Nicely done. – Dragonrage Mar 28 '18 at 2:26

Across

5. COSMIC (COMICS)

Down

1. COVERT (VECTOR)
2. HARDEST HATREDS (either works)
3. MUTILATE ULTIMATE (either works)

• see my edit for 2 down. – Dragonrage Mar 27 '18 at 22:07
• @Dragonrage: Gotcha. Updated my answer for that. – gnovice Mar 27 '18 at 23:08

It might be a stretch, but for 7 Across using Rupert's pattern:

CHARMER/MARCHER*

• I'm going to put it in and call the puzzle done. – Rupert Morrish Mar 28 '18 at 2:02
• Your answers are also anagrams of each other! $(+1)$ :P – Mr Pie Sep 11 '18 at 5:23

4 Down (thin expensive ore pieces) might be

Bangles
Bangles are thin bracelets made from precious metals (smelted from ore)

• The only definition I am finding for 4 down is a bracelet of some sort - how are you connecting it to ore? – Jordan.J.D Mar 27 '18 at 19:01
• @Jordan.J.D See edit. – Selvek Mar 27 '18 at 19:29
• Thanks for the upvotes... but it looks like I was waaay off :) – Selvek Mar 27 '18 at 22:52