Six-stringed instrument (6)
I believe the answer is:
guitar
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">six-stringed instrument</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for guitar that I've seen before include "One played with plectrum" , "Axe" , "Popular stringed musical instrument" , "Stringed instrument often played by pop groups" , "Plucked instrument" .)