Viewing organ (3)
I believe the answer is:
eye
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">viewing organ</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for eye that I've seen before include "Globular organ" , "Location of 11dn" , "Organ of vision" , "Regard" , "'Public' or 'private' body part" .)