Odd bits of charm in English river (3)
I believe the answer is:
cam
'english river' is the definition.
(river in Cambridge)
'odd bits of charm' is the wordplay.
'odd bits of' means one should take alternating letters.
The alternating letters of 'charm' are 'CAM'.
'in' acts as a link.
(Other definitions for cam that I've seen before include "Eccentric contrivance" , "Bump on a shaft for pushing another shaft" , "Projection on rotating cylinder" , "Reciprocal-motion part" , "East Anglian river" .)