Deity with 99 names (5)
I believe the answer is:
allah
'deity with 99 names' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for allah that I've seen before include "God worshipped in 5 Across" , "God of the Muslims" , "Divinity" , "Muslim and Arab name of God" , "God in Islam" .)