Synthetic resin or plastic (5)
I believe the answer is:
vinyl
I believe this clue is a double definition.
'synthetic resin' is the first definition.
(I've seen this before)
'plastic' is the second definition.
(I know that vinyl is a type of plastic)
(Other definitions for vinyl that I've seen before include "Old record material" , "Synthetic polymer" , "Shiny, tough and flexible material used for floor coverings" , "Synthetic plastic" , "LP material" .)