Chimera (8)
I believe the answer is:
illusion
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">chimera</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for illusion that I've seen before include "Chimera" , "A false belief about linus oil" , "Deceptive impression" , "Subjects under discussion" , "False vision or mirage (8)" .)