"Amadeus" antagonist (7)
I believe the answer is:
salieri
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">amadeus antagonist</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 salieri that I've seen before include "Rival of Mozart" , "Composer contemporary with Mozart" , "Italian composer" , "musician accused of murder" .)