Surprising sight (3-6)
I believe the answer is:
eye-opener
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">surprising sight</span>' is the definition.<br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for eye-opener that I've seen before include "Fact that brings great surprise, dilating optics" , "Startling thing" , "Unexpected revelation" , "A startling enlightenment!" , "Startling revelation" .)