Holy circle of light (4)
I believe the answer is:
halo
'holy circle of light' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for halo that I've seen before include "Ring (around sun or moon)" , "Circle of light round the sun or moon" , "Band of light" , "Angelic aura" , "Circle over saint's head in painting" .)