So back to flag an Egyptian god (6)
I believe the answer is:
osiris
'an egyptian god' is the definition.
(Osiris is an example)
'so back to flag' is the wordplay.
'back' is a reversal indicator.
'to flag' becomes 'iris' ('iris' can be a synonym of 'flag').
'so' backwards is 'os'.
'os'+'iris'='OSIRIS'
(Other definitions for osiris that I've seen before include "one held to be divine" , "Egyptian god of the dead" , "Egyptian deity" , "Egyptian god of the underworld" , "one Egyptians worshipped" .)