Mirage (8)
I believe the answer is:
illusion
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mirage</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 illusion that I've seen before include "Subjects under discussion" , "Wrong belief or fancy, may be optical" , "False idea or conjuring trick" , "False impression" , "Deceptive impression" .)