The most common and most likely answer to this crossword clue is the 3 letter word URE
I've seen this crossword clue in The Times
U
R
E
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 URE mean?
URE noun- (only in collocations in ure, out of ure) use, practise, exercise.
- To use; to exercise; to inure; to accustom by practice.