The most common and most likely answer to this crossword clue is the 4 letter word LUNE
I've seen this crossword clue in The Daily Telegraph
L
U
N
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 LUNE mean?
LUNE noun- A fit of lunacy or madness; a period of frenzy; a crazy or unreasonable freak.
- A concave figure formed by the intersection of the arcs of two circles on a plane, or on a sphere the intersection between two great semicircles.
- Anything crescent-shaped.
- (hawking) A leash for a hawk.