Subject, topic (5)
I believe the answer is:
theme
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">subject</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(theme can mean a topic or subject)</span><br/ ><br/ >'<span class="explanation-format__original">topic</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for theme that I've seen before include "Musical motif" , "Unifying motif" , "Motif - 4 across" , "notedly subject to variation" , "He met (anag) - subject" .)