Tailor only after northern fabric (5)
I believe the answer is:
nylon
'fabric' is the definition.
(nylon is a kind of fabric)
'tailor only after northern' is the wordplay.
'tailor' indicates anagramming the letters (I've seen this in other clues).
'after' says to put letters next to each other.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'only' anagrammed gives 'nylo'.
'nylo'+'n'='NYLON'
(Other definitions for nylon that I've seen before include "Artificial yarn/fabric" , "Tights material" , "Artific ial (stocking) material" , "Yarn for stockings" , "Stocking; polymer" .)