A high explosive (8)
I believe the answer is:
dynamite
'a high explosive' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for dynamite that I've seen before include "High explosive" , "might one be blown away by it?" , "Tiny dame (anag)" , "Spectacular (or dangerous) person (or thing)" , "an exciting thing" .)