Any longer trousers material? (5)
I believe the answer is:
nylon
'material?' is the definition.
(nylon is a kind of material)
'any longer trousers' is the wordplay.
'trousers' indicates the answer is hidden within the clue (to trouser can mean to contain or hold).
'NYLON' is hidden in the letters of 'any longer'.
(Other definitions for nylon that I've seen before include "Type of material" , "Yarn for stockings" , "Synthetic fabric invented in 1938" , "where ladder can appear?" , "Fibrous material" .)