City that's large and on a river (6)
I believe the answer is:
london
'city' is the definition.
(London is an example)
'large and on a river' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'and' says to put letters next to each other.
'a river' becomes 'Don' (Don is an example).
'l'+'on'+'don'='LONDON'
'that's' is the link.
(Other definitions for london that I've seen before include "- Clay; - pride; - plane" , "Home of Cockney" , "source of this paper" , "UK's capital" , "UK Capital city" .)