Incendiary weapon (6)
I believe the answer is:
napalm
'incendiary weapon' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for napalm that I've seen before include "Incendiary bomb ingredient" , "Does Ma plan to use the sticky jelly in fire bombs?" , "Chemical weapon" , "Flame thrower ingredient" , "Petrol jelly used in flame-throwers" .)