Name on the Saudi flag (5)
I believe the answer is:
allah
'name on the saudi flag' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for allah that I've seen before include "God worshipped in 5 Across" , "God of the Muslims" , "Muslim supreme being" , "God in Islam" , "God of the Arabs" .)