Departs with nun, frolicking in Y-fronts? (10)
I believe the answer is:
underpants
'y-fronts?' is the definition.
(Y-fronts are a type of underwear)
'departs with nun frolicking' is the wordplay.
'with' is a charade indicator (letters next to each other).
'frolicking' is an anagram indicator.
'departs'+'nun'='departsnun'
'departsnun' anagrammed gives 'UNDERPANTS'.
'in' acts as a link.
(Other definitions for underpants that I've seen before include "Close-fitting garment" , "Intimate clothing" , "Shorts" , "drawers" , "cover and support" .)