This is not a typical construction - part of the solving process of this crossword is figuring out what that means.
Some signs that this is part of the "theme" of the puzzle:
- Theme entries are typically long Across entries; there aren't any extremely long Across entries, and all the clues that have that are Across entries.
- These entries don't make sense as answers to their clues (or at all, for that matter).
- Clue 11-Down says "Carnival game represented in this puzzle". Clues referencing "this puzzle" typically imply that there is something unusual going on in the puzzle (likely multiple instances of it!), where the answers to clues are entered in unusual ways.
Here, 11-Down is WHACK-A-MOLE. So you're likely looking for things representing "moles" in the grid. Hey, the referenced Down entries all have MOLE
in them as a substring!

And not only that, each of them is "sticking up" from its corresponding confusing Across clue!
So, if you "whack" those MOLE
s back down into their lowest square, the Across entries make much more sense - they're DNA MOLECULE
, DEMO LESSON
, and KGB MOLE
.
These types of themes appear often in crosswords - in daily publications like the New York Times, they're particularly common in Thursday and Sunday puzzles. The puzzle "Magic Tricks" by Eric Berlin, reviewed here, shows off some other somewhat common gimmicks (a rebus square, missing letters, and letters extending outside of the grid).