The most common and most likely answer to this crossword clue is the 4 letter word GIRN
I've seen this crossword clue in Independent
G
I
R
N
Buddy explains!

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 GIRN mean?
GIRN noun- A vocalization similar to a cat's purring.
- To grimace; to snarl.
- To whinge, moan, complain.
- To make elaborate unnatural and distorted faces as a form of amusement or in a girning competition.