Enigmatic (10)
I believe the answer is:
mysterious
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">enigmatic</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for mysterious that I've seen before include "Inexplicable" , "Spooky" , "Strange" , "Beyond normal understanding" , "Secret" .)