Symbol of saintliness (4)
I believe the answer is:
halo
'symbol of saintliness' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for halo that I've seen before include "Sign of a saint" , "Light around sun, saint" , "Corona" , "Hagiological aura featured in Christian art" , "Circle of light around the moon" .)