Tough fabric (5)
I believe the answer is:
denim
'tough fabric' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for denim that I've seen before include "Cotton twill fabric" , "Material for casual trousers or jackets" , "Hard-wearing clothing material, twilled cotton" , "Hard-wearing cloth" , "dark blue material" .)