Dug up then sent back this material (5)
I believe the answer is:
denim
'sent back this material' is the definition.
'denim' can be an answer for 'material' (type of fabric). I'm unsure of the rest of the definition.
'dug up' is the wordplay.
'dug' becomes 'mined' (dug into the ground).
'up' is a reversal indicator (in down clue: letters go upwards).
'mined' written backwards gives 'DENIM'.
'then' acts as a link.
Can you help me to learn more?
(Other definitions for denim that I've seen before include "dark blue material" , "maker of jeans" , "Cloth for jeans, etc" , "Coloured cotton twill" , "Coarse durable twill-weave cotton fabric" .)