Newton only tailored material (5)
I believe the answer is:
nylon
'material' is the definition.
(nylon is a kind of material)
'newton only tailored' is the wordplay.
'newton' becomes 'N' (synonyms).
'tailored' is an anagram indicator (the letters are customised ).
'only' anagrammed gives 'ylon'.
'n'+'ylon'='NYLON'
(Other definitions for nylon that I've seen before include "Hosiery material" , "Plastic used for stockings" , "Artific ial (stocking) material" , "A thermoplastic" , "Artificial fibre" .)