Material about to be dug up
I believe the answer is:
mined
'be dug up' is the definition.
(I've seen this in another clue)
'material about' is the wordplay.
'material' becomes 'denim' (type of fabric).
'about' is a reversal indicator.
'denim' in reverse letter order is 'MINED'.
'to' acts as a link.
(Other definitions for mined that I've seen before include "Extracted minerals from the earth" , "proceeded secretly" , "laid eggs" , "Dug for minerals, say coal" , "Sought diamonds?" .)