Smelly explosive (5,4)
I believe the answer is:
stink bomb
(Other definitions for stink bomb that I've seen before include "Malodorous pellet" , "Foul-smelling object used by practical jokers" , "Device containing sulphurous matter traditionally loved by naughty boys" , "Prankster's smelly explosive" , "Smelly device let off by a schoolboy" .)