Secrets, mysteries (6)
I believe the answer is:
arcana
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">secrets</span>' is the first definition.<br/ ><span class="explanation-format__explanation">('arcanum' can be a synonym of 'secret')</span><br/ ><br/ >'<span class="explanation-format__original">mysteries</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for arcana that I've seen before include "Secrets, mysteries" , "Secret things" , "Tarot cards" .)