Believer cross at robbery (6)
I believe the answer is:
theist
'believer' is the definition.
(someone who believes in a god)
'cross at robbery' is the wordplay.
'cross' becomes 'T' (shape).
'at' means one lot of letters go next to another.
'robbery' becomes 'heist' (heist is a kind of robbery).
't'+'heist'='THEIST'
(Other definitions for theist that I've seen before include "Tithes (anag.)" , "Person in good faith" , "Tithes for believer in God" , "One who believe in a god" , "Believer in a creator god" .)