Tartan trousers (5)
I believe the answer is:
trews
'tartan trousers' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for trews that I've seen before include "Trousers of a Scot" , "Garment" , "Wrest (anag) - trousers" , "nether garments" , "close-fitting garments" .)