Boy soprano (6)
I believe the answer is:
treble
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">boy soprano</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 treble that I've seen before include "Multiply by three - high-pitched" , "Singer; in three parts" , "large measure" , "Threefold; boy's voice" , "Very big drink" .)