Slender sword (6)
I believe the answer is:
rapier
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">slender sword</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for rapier that I've seen before include "Light sword" , "fencing equipment" , "A thin double-edged sword" , "Straight sword with narrow blade" , "Sword for thrusting" .)