Only altered new fabric (5)
I believe the answer is:
nylon
'fabric' is the definition.
(nylon is a kind of fabric)
'only altered new' is the wordplay.
'altered' indicates an anagram.
'new' becomes 'n'.
'only' with letters rearranged gives 'nylo'.
'nylo'+'n'='NYLON'
(Other definitions for nylon that I've seen before include "Strong, resilient, synthetic fibre" , "Fibrous material" , "Man-made material" , "Man-made fabric" , "Artificial fabric" .)