Material put under copper (5)
I believe the answer is:
plaid
'material' is the definition.
(I know that plaid is a type of material)
'put under copper' is the wordplay.
'put' becomes 'laid' (I've seen this before).
'under' says to put letters next to each other.
'copper' becomes 'p'.
'laid' after 'p' is 'PLAID'.
(Other definitions for plaid that I've seen before include "party in Wales" , "woollen cloth" , "Tartan twill cloth" , "Tartan patterned cloth" , "Tartan-pattern cloth" .)