Countertenor (4)
I believe the answer is:
alto
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">countertenor</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for alto that I've seen before include "One who sings" , "Lowest female singing voice" , "Member of choir" , "The highest adult male singing-voice" , "someone to sing" .)