Faculty of sight (6)
I believe the answer is:
vision
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">faculty of sight</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 vision that I've seen before include "Ability to see (6)." , "Perception by eye" , "Power of sight" , "Forward plan" , "Sight or insight" .)