Vehicle's way over left side of carriageway, by a river (9)
I believe the answer is:
streetcar
'left side of carriageway by a river' is the definition.
I can't tell whether this defines the answer.
'vehicle's way over' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle).
'way' becomes 'street' (street is a kind of way).
'over' says to put letters next to each other (in a down clue, some letters go over others).
'car' put after 'street' is 'STREETCAR'.
Can you help me to learn more?
(Other definitions for streetcar that I've seen before include "Tennessee Williams play 'A . . . . . . . . . Named Desire'" , "US tram (named Desire?)" , "public transport?" , ""Desire" was one" , "Desire, perhaps" .)