Something syrupy to drop in explosive device (7)
I believe the answer is:
grenade
'explosive device' is the definition.
(grenade is a kind of explosive device)
'something syrupy to drop in' is the wordplay.
'something syrupy' becomes 'grenadine'.
'to drop' suggests deleting specific letters.
'grenadine' with 'in' taken out is 'GRENADE'.
(Other definitions for grenade that I've seen before include "Enraged (anag)" , "Small bomb thrown by hand" , "Small explosive device" , "hand-held missile" , "Handy bomb" .)