Plastic explosive (6)
I believe the answer is:
semtex
'plastic explosive' is the definition.
(I know that semtex is a plastic explosive)
This is the entire clue.
(Other definitions for semtex that I've seen before include "Plastic explosive from the Czech Republic" , "Explosive material used by terrorists" , "Type of plastic explosive" , "Explosive substance used by terrorists" , "Plastic explosive used by terrorists" .)