Dismiss function as explosive (8)
I believe the answer is:
firework
'explosive' is the definition.
(I know that firework is a type of low explosive)
'dismiss function' is the wordplay.
'dismiss' becomes 'fire' (synonyms).
'function' becomes 'work' (synonyms).
'fire'+'work'='FIREWORK'
'as' is the link.
(Other definitions for firework that I've seen before include "Banger, for example" , "Pyrotechnic device" , "Colourful incendiary device used for entertainment" , "fountain, say" , "rocket" .)