Crews on either side of English river (6)
I believe the answer is:
ganges
'river' is the definition.
(Ganges River is an example)
'crews on either side of english' is the wordplay.
'crews' becomes 'gangs' ('gang' can be a synonym of 'crew').
'on either side of' indicates putting letters inside.
'english' becomes 'E' (abbreviation as in OED).
'gangs' going around 'e' is 'GANGES'.
(Other definitions for ganges that I've seen before include "Holy Indian river" , "Asian flower" , "River flowing into the Bay of Bengal" , "Hindus' most sacred river" , "Great river of India" .)