Prince given ring, a symbol of saintliness (4)
I believe the answer is:
halo
'a symbol of saintliness' is the definition.
(I've seen this in another clue)
'prince given ring' is the wordplay.
'prince' becomes 'hal' (Shakespearean nickname of Henry V when a prince).
'given' is a charade indicator (letters next to each other).
'ring' becomes 'O' (letter resembling a ring).
'hal'+'o'='HALO'
(Other definitions for halo that I've seen before include "Luminous sign of saintliness" , "that could make one light-headed?" , "Circle over a saint" , "Aureole" , "Imaginary circle over saint's head" .)