Only working with new material (5)
I believe the answer is:
nylon
'material' is the definition.
(I know that nylon is a type of material)
'only working with new' is the wordplay.
'working with' indicates anagramming the letters (working with the letters).
'new' becomes 'n' (abbreviation as in New Testament NT).
'only' anagrammed gives 'nylo'.
'nylo'+'n'='NYLON'
(Other definitions for nylon that I've seen before include "Polyamide" , "Artificial fabric" , "Tough synthetic material" , "Artificial yarn/fabric" , "Hose" .)