Vehicle taking unusual route alongside river (6)
I believe the answer is:
tourer
'vehicle' is the definition.
(tourer is a kind of vehicle)
'unusual route alongside river' is the wordplay.
'unusual' is an anagram indicator.
'alongside' is a charade indicator (letters next to each other).
'river' becomes 'r' (**).
'route' is an anagram of 'toure'.
'toure'+'r'='TOURER'
'taking' acts as a link.
(Other definitions for tourer that I've seen before include "Vehicle" , "Car for travellers" , "Car for holiday trip" , "Large open car with folding top" , "Large motor car" .)