God thus rejected goddess (6)
I believe the answer is:
osiris
'god' is the definition.
(Egyptian god)
'thus rejected goddess' is the wordplay.
'thus' becomes 'so' (synonyms).
'rejected' says the letters should be written backwards.
'goddess' becomes 'iris' (Greek goddess of the rainbow).
'so' back-to-front is 'os'.
'os'+'iris'='OSIRIS'
(Other definitions for osiris that I've seen before include "Egyptian god of the dead" , "God, husband of Isis" , "Egyptian god - sis or I (anag)" , "once highly esteemed by Egyptians" , "Egyptian deity" .)