Opera highlight (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">opera highlight</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 "Musical performance" , "Song such as "Your Tiny Hand is Frozen"" , "Operatic song" , "Song from an opera (4)" , "Operatic tune" .)