Explosive category including topless men (7)
I believe the answer is:
grenade
'explosive' is the definition.
(I've seen this before)
'category including topless men' is the wordplay.
'category' becomes 'grade'.
'including' is an insertion indicator.
'topless' means to remove the first letter.
'men' with its initial letter removed is 'en'.
'grade' enclosing 'en' is 'GRENADE'.
(Other definitions for grenade that I've seen before include "Pineapple" , "Hand-thrown bomb" , "hand-held missile" , "Missile thrown" , "Small hand-bomb" .)