Short musical drama (8)
I believe the answer is:
operetta
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">short musical drama</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for operetta that I've seen before include "Light opera" , "The Mikado or The Gondoliers, say" , "The Merry Widow, for example" , "Short amusing opera" , "Type of musical drama" .)