Short knife (6)
I believe the answer is:
dagger
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">short knife</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for dagger that I've seen before include "Murder weapon" , "that has an incisive point" , "Hand weapon" , "'Short, double-edged blade (6)'" , "Macbeth's weapon" .)