Material that may be mined (5)
I believe the answer is:
denim
'material' is the definition.
(type of fabric)
'may be mined' is the wordplay.
'may be' indicates an anagram.
'mined' with letters rearranged gives 'DENIM'.
'that' is the link.
(Other definitions for denim that I've seen before include "Tough cotton fabric" , "Durable material" , "Twilled cotton fabric" , "Coloured cotton twill" , "dark blue material" .)