God of the rosary (4)
I believe the answer is:
eros
'god' is the definition.
(I know that Eros is a god)
'of the rosary' is the wordplay.
'of' says the answer is hidden in the clue.
'EROS' is hidden in the letters of 'the rosary'.
(Other definitions for eros that I've seen before include "Goddess" , "London landmark" , "Deity" , "One worshipped" , "Greek name of Cupid" .)