God, in Arabic (5)
I believe the answer is:
allah
'god in arabic' 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 in Islam" , "Muslim and Arab name of God" , "God worshipped in 5 Across" , "God of the Muslims" , "Muslim supreme being" .)