Vocal piece (7)
I believe the answer is:
cantata
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vocal piece</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 cantata that I've seen before include "Sacred choral piece" , "musical form?" , "Choral item" , "Vocal work with orchestra" , "aria" .)