The explosive has more writhing in agony (7)
I believe the answer is:
torment
'agony' is the definition.
(synonyms)
'the explosive has more writhing' is the wordplay.
'the explosive' becomes 'tnt' (TNT is an example).
'has' indicates putting letters inside.
'writhing' indicates anagramming the letters.
'more' anagrammed gives 'orme'.
'tnt' enclosing 'orme' is 'TORMENT'.
'in' acts as a link.
(Other definitions for torment that I've seen before include "Cause mental distress" , "Harass" , "Extreme mental or physical distress" , "Badger" , "Hound" .)