Strong glue (5)
I believe the answer is:
epoxy
'strong glue' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for epoxy that I've seen before include "Type of resin" , "Synthetic adhesive, paint etc." , "Synthetic resin used as glue" , "Adhesive; plastic" , "Type of adhesive/paint" .)