The most common and most likely answer to this crossword clue is the 4 letter word GELS
G
E
L
S
More clues leading to the result GELS
Buddy explains!

The straight part
We know that "Sets" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sets = gels.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does GELS mean?
GELS noun- A semi-solid to almost solid colloid of a solid and a liquid, such as jelly, cheese or opal.
- Any gel intended for a particular cosmetic use, such as for styling the hair.
- To apply (cosmetic) gel to (the hair, etc).
- To become a gel.
- To develop a rapport.
- A girl.