Hyperbole (8)
I believe the answer is:
overkill
'hyperbole' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for overkill that I've seen before include "Hyperbole" , "Action far more drastic than necessary" , "Excessive action, armament" , "much more than required" , "Excessive effort for task - sounds deadly" .)