Explode without full force? That's a mistake (4)
I believe the answer is:
goof
'that's a mistake' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
(Other definitions for goof that I've seen before include "In slang, bungle or blunder" , "Foolish mistake" , "boob" , "Blunder, mistake (slang)" , "foolish error" .)