Arcane matters (7)
I believe the answer is:
esotery
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">arcane matters</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 esotery that I've seen before include "Secret doctrine" , "Rare doctrine" .)