"Rigoletto" solo (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rigoletto solo</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for aria that I've seen before include "Elaborate accompanied song for solo voice" , "Air in an opera" , "Song, one from 'West Side Story' needing no introduction" , "Nessun Dorma, for example" , "Refrain" .)