Ring of light (4)
I believe the answer is:
halo
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ring of light</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 halo that I've seen before include "Light around sun, saint" , "Aureole" , "Disc of light" , "Band of light" , "Circle painted over saint's head" .)