Made money when unopened grenade exploded (6)
I believe the answer is:
earned
'made money' is the definition.
(I've seen this in another clue)
'unopened grenade exploded' is the wordplay.
'unopened' means to remove the first letter (without opening letter).
'exploded' indicates anagramming the letters.
'grenade' with its first letter removed is 'renade'.
'renade' is an anagram of 'EARNED'.
'when' is the link.
(Other definitions for earned that I've seen before include "Acquired through work or effort" , "Gained by working" , "Obtained through work" , "Merited; made" , "made money" .)