Unable to see (5)
I believe the answer is:
blind
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unable to see</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 blind that I've seen before include "Unaware of" , "Unable to see - screen" , "Unable to observe" , "deception" , "shade" .)