Kind of clef (6)
I believe the answer is:
treble
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">kind of clef</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 treble that I've seen before include "Hit in inner ring of dartboard" , "Chorister; multiply by three" , "High voice - large drink" , "winning series" , "large measure" .)