Sign of sainthood
I believe the answer is:
halo
'sign of sainthood' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for halo that I've seen before include "Circle of light round the sun or moon" , "Circle over saint's head in painting" , "Ring of light (signifying holiness)" , "Ring (around sun or moon)" , "Disc of light" .)