Twilled fabric used in looser gear (5)
I believe the answer is:
serge
'twilled fabric' is the definition.
(I've seen this before)
'in looser gear' is the wordplay.
'in' says the answer is hidden in the clue.
'SERGE' is hidden within 'looser gear'.
'used' is the link.
(Other definitions for serge that I've seen before include "Stuff" , "Strong twilled worsted fabric" , "Material to suit" , "A twill fabric" , "Frenchman" .)