Convertible taxi finds river is rented (9)
I believe the answer is:
cabriolet
'convertible' is the definition.
(I've seen this before)
'taxi finds river is rented' is the wordplay.
'taxi' becomes 'cab' (synonyms).
'finds' is a charade indicator (letters next to each other).
'river' becomes 'rio' ('river' in Spanish).
'is rented' becomes 'let' (I've seen this before).
'cab'+'rio'+'let'='CABRIOLET'
(Other definitions for cabriolet that I've seen before include "Car with a folding roof" , "Car with a folding top -- trace boil (anag)" , "convertible" , "Light two-wheeled carriage" , "Horse-drawn carriage with two seats and a folding hood" .)