Against having to travel on river (5)
I believe the answer is:
congo
'river' is the definition.
(Congo is an example)
'against having to travel' is the wordplay.
'against' becomes 'con' (I've seen this before).
'having' means one lot of letters go next to another.
'to travel' becomes 'go' ('go' can be a synonym of 'travel'**).
'con'+'go'='CONGO'
'on' is the link.
(Other definitions for congo that I've seen before include "African river and region" , "flower" , "African runner" , "Africa's second longest river" , "African republic" .)