Power of vision (8)
I believe the answer is:
eyesight
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">power of vision</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 eyesight that I've seen before include "What's needed to see" , "Purpose of certain organs" , "perception" , "Requirement to look" , "Power of vision" .)