Knife for stabbing (6)
I believe the answer is:
dagger
'knife for stabbing' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for dagger that I've seen before include "A weapon; a reference mark" , "Stabbing weapon" , "that has an incisive point" , "Short knife for stabbing" , "''Is this a ... which I see before me'' (Macbeth)" .)