Composition for two (4)
I believe the answer is:
duet
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">composition for two</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 duet that I've seen before include "Piece for brace" , "Paired performance" , "Two singers performing together" , "Work for two performers" , "Performance by company, perhaps" .)