The most common and most likely answer to this crossword clue is the 2 plus 3 plus 3 plus 4 letter word IF THE CAP FITS
I
F
T
H
E
C
A
P
F
I
T
S
Buddy explains!
The straight part
We know that "Fine to wear, when cooking, is it apt, chef?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fine to wear, when cooking, is it apt, chef? = if the cap fits.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.