Explosive mixture (9)
I believe the answer is:
gunpowder
'explosive mixture' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gunpowder that I've seen before include "Explosive; type of 23 dn" , "It's used in gunnery and fireworks" , "Oldest known explosive" , "Explosive chemical mixture" , "plot? Sort of" .)