Cathedral city in Cambridgeshire on the River Ouse (3)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
ely
(Other definitions for ely that I've seen before include "Diocese in Eastern England" , "Cathedral city in East Anglia" , "Fenland cathedral town" , "Cambs. city" , "Small city in Cambridgeshire" .)