City on the River Avon (7)
I believe the answer is:
bristol
'city on the river avon' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for bristol that I've seen before include "Port; such fashion is in good order" , "Port and industrial city in southwest England" , "West Country city" , "A port; neat (fashion)" , "English city" .)