The most common and most likely answer to this crossword clue is the 9 plus 4 letter word MOONLIGHT FLIT
I've seen this crossword clue in The Times
M
O
O
N
L
I
G
H
T
F
L
I
T
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.