Material may be mined (5)

I believe the answer is:

denim

'material' is the definition.
(denim is a kind of material)

'may be mined' is the wordplay.
'may be' indicates anagramming the letters.
'mined' anagrammed gives 'DENIM'.

(Other definitions for denim that I've seen before include "Coarse durable twill-weave cotton fabric" , "Hard-wearing blue fabric" , "Cotton twill fabric" , "dark blue material" , "Hard-wearing cotton fabric" .)

I've seen this clue in the Evening Standard.

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