Material I mend, if damaged (5)
I believe the answer is:
denim
'material' is the definition.
(type of fabric)
'i mend if damaged' is the wordplay.
'if damaged' is an anagram indicator.
'i'+'mend'='imend'
'imend' with letters rearranged gives 'DENIM'.
(Other definitions for denim that I've seen before include "Coarse durable twill-weave cotton fabric" , "Twill cloth" , "Mined badly for a hard-wearing fabric" , "Hard-wearing cloth" , "Material for casual trousers or jackets" .)