Harold only gets saintly sign (4)
I believe the answer is:
halo
'saintly sign' is the definition.
(I've seen this in another clue)
'harold only' is the wordplay.
'harold' becomes 'Hal' (diminutive, as in Hal Prince).
'only' becomes 'o' (this might be a standard abbreviation I've not previously seen).
'hal'+'o'='HALO'
'gets' is the link.
Can you help me to learn more?
(Other definitions for halo that I've seen before include "Glittering aura" , "Circle of light around the moon" , "Luminous ring" , "overhead lighting?" , "This indicates holiness" .)