Angel topper (4)
I believe the answer is:
halo
'angel topper' 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 "Symbol of sainthood" , "Circle of light round the sun or moon" , "Ring of saintliness" , "Circle of light around the moon" , "Ring of light round head" .)