Groups crossing English river (6)

I believe the answer is:
ganges
'river' is the definition.
(I know that Ganges is a river)
'groups crossing english' is the wordplay.
I cannot quite understand how this works, but
'english' could be 'e' (abbreviation as in OED) and 'e' is found within the answer.
The remaining letters 'gangs' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ganges that I've seen before include "Hindus' most sacred river" , "Asian flower" , "Holy water" , "Sacred river of N India" , "Sacred Hindu river in India" .)
