Twilled fabric used in coarser gear (5)
I believe the answer is:
serge
'twilled fabric' is the definition.
(type of fabric)
'in coarser gear' is the wordplay.
'in' indicates a hidden word.
'SERGE' is hidden within 'coarser gear'.
'used' is the link.
(Other definitions for serge that I've seen before include "Durable fabric" , "A twill fabric" , "Twilled woollen fabric" , "Frenchman" , "Stuff" .)