Lot of money for a weapon (4)
I believe the answer is:
bomb
This clue is a double definition.
'lot of money' is the first definition.
(I've seen this before)
'a weapon' is the second definition.
(I have seen 'Explosive weapon ' mean 'bomb' so perhaps 'weapon' could also mean 'bomb')
'for' is the link.
(Other definitions for bomb that I've seen before include "Great deal of money (slang)" , "move quickly" , "One set off" , "Exploding weapon" , "Exploding device" .)