Implement to kill or injure (6)
I believe the answer is:
weapon
'implement to kill or injure' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for weapon that I've seen before include "Implement used to inflict bodily harm" , "missile perhaps" , "Thing used to inflict bodily harm" , "club, perhaps" , "A tool for inflicting injury" .)