Some underwear shows outlines (6)
I believe the answer is:
briefs
This clue is a double definition.
'some underwear' is the first definition.
(I've seen this before)
'outlines' is the second definition.
(brief is a kind of outline)
'shows' acts as a link.
(Other definitions for briefs that I've seen before include "Garments" , "Case summaries drawn up for barristers" , "Underwear and lawyer's documents" , "Close-fitting underpants" , "Pants" .)