Piece of stout terylene, say (5)
I believe the answer is:
utter
'say' is the definition.
(thesaurus)
'piece of stout terylene' is the wordplay.
'piece of' indicates the answer is hidden within the clue.
'UTTER' can be found hidden inside 'stout terylene'.
(Other definitions for utter that I've seen before include "Put into words" , "Express audibly" , "Dead" , "To say, articulate" , "Say; total" .)