Slow charge lit to explode (9)
I believe the answer is:
lethargic
'slow' is the definition.
(I've seen this before)
'charge lit to explode' is the wordplay.
'to explode' indicates anagramming the letters.
'charge'+'lit'='chargelit'
'chargelit' with letters rearranged gives 'LETHARGIC'.
(Other definitions for lethargic that I've seen before include "Sluggish and apathetic" , "reluctant to move" , "Listless" , "lack of energy" , "The garlic (anag.)" .)