Close-fitting underpants (6)
I believe the answer is:
briefs
'close-fitting underpants' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for briefs that I've seen before include "Underwear and lawyer's documents" , "Instructs a barrister" , "Digests" , "Garments" , "They are prepared for barristers' perusal" .)