Optical toy (12)
I believe the answer is:
kaleidoscope
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">optical toy</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 kaleidoscope that I've seen before include "colourful viewer" , "Diverse variety of sights" , "Toy making coloured patterns" , "A changing pattern of colours, shapes" , "Optical pattern-making toy" .)