God in London district creates atmospheric effect (7)
I believe the answer is:
rainbow
'atmospheric effect' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'god in london district' is the wordplay.
'god' becomes 'Ra' (Egyptian god).
'london district' becomes 'Bow' (area of London).
'ra'+'in'+'bow'='RAINBOW'
'creates' is the link.
Can you help me to learn more?
(Other definitions for rainbow that I've seen before include "Wide range of colours" , "weather feature" , "illusory hope?" , "All the colours of the spectrum" , "heavenly sight" .)