Stabbing weapon (6)
I believe the answer is:
dagger
'stabbing weapon' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for dagger that I've seen before include "Murder weapon" , "Macbeth's weapon" , "Stabbing weapon" , "that has an incisive point" , "''Is this a ... which I see before me'' (Macbeth)" .)