Polluted river in which crew's emptied effluents (6)

I believe the answer is:

ganges

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'polluted river' is the definition.
'Ganges' can be an answer for 'river' (Ganges River is an example). I'm not sure about the 'polluted' bit.

'crew's emptied effluents' is the wordplay.
'crew' becomes 'gang' (synonyms).
'emptied' suggests removing the centre.
'effluents' with its middle removed is 'es'.
'gang'+'es'='GANGES'

'in which' is the link.

Can you help me to learn more?

(Other definitions for ganges that I've seen before include "Indian flower" , "Great river of India" , "Sacred river of N India" , "Sacred Indian river" , "Sacred Hindu river in India" .)

I've seen this clue in The Guardian.

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