Mother's involved with plan for making bombs (6)
I believe the answer is:
'mother's' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for napalm that I've seen before include "Incendiary jelly used in flamethrowers" , "Incendiary liquid used in firebombs" , "destroy by fire" , "Highly flammable jelly" , "Petroleum jelly used in bombs and flame-throwers" .)