Light refractor (5)
I believe the answer is:
prism
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">light refractor</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for prism that I've seen before include "Cut-glass object" , "Female character in The Importance of Being Ernest -- optical device" , "Triangular piece of glass, optical device" , "source of colourful viewing?" , "Refracting glass" .)