A twilled woollen fabric (5)
I believe the answer is:
serge
'a twilled woollen fabric' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for serge that I've seen before include "Twilled woollen fabric" , "Twilled fabric; name" , "Frenchman" , "A twill fabric" , "Stuff" .)