Disguise
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">disguise</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that mask is a kind of disguise)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for mask that I've seen before include "False face" , "Cover for the face" , "One hiding, protecting face" , "Face-covering" , "Camouflage" .)