One-ply tyres can be moulded from this synthetic resin (11)
I believe the answer is:
polystyrene
'moulded from this synthetic resin' is the definition.
'polystyrene' can be an answer for 'synthetic resin' (polystyrene is a kind of synthetic resin). I am not certain of the remainder of the definition.
'one-ply tyres can be' is the wordplay.
'can be' is an anagram indicator.
'one'+'ply'+'tyres'='oneplytyres'
'oneplytyres' is an anagram of 'POLYSTYRENE'.
Can you help me to learn more?
(Other definitions for polystyrene that I've seen before include "Hard plastic" , "Synthetic material - let nosey pry (anag)" , "Synthetic resin used in packing" , "Lightweight synthetic material" , "Synthetic resin for packing, insulation" .)