Subject matter (5)
I believe the answer is:
theme
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">subject matter</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that theme is a type of subject matter)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for theme that I've seen before include "Subject; recurring idea" , "Thread, melody" , "(Writer's) topic" , "Subject of a talk or piece of writing" , "Motif - 4 across" .)