Northbound river in less empty city (5)
I believe the answer is:
leeds
'city' is the definition.
(city in England)
'northbound river in less empty' is the wordplay.
'northbound' shows that the letters should be reversed in order.
'river' becomes 'dee' (River Dee).
'in' indicates putting letters inside.
'empty' means to remove the middle letters.
'less' with its centre removed is 'ls'.
'dee' back-to-front is 'eed'.
'eed' put within 'ls' is 'LEEDS'.
(Other definitions for leeds that I've seen before include "West Yorkshire city" , "22 [FA CUP] runners-up" , "English city" , "W Yorkshire city" , "City on River Aire" .)