The most common and most likely answer to this crossword clue is the 3 letter word MIM
I've seen this crossword clue in The Guardian
M
I
M
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 MIM mean?
MIM adjective- Demure, shy.
- The letter م in the Arabic script.