Scratching both sides, curse wide vehicle (3)

I believe the answer is:
bus
'vehicle' is the definition.
(public transport vehicle)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for bus that I've seen before include "Means of public transport" , "eg Double-decker" , "Public transport vehicle" , "Something caught" , "Public service vehicle" .)
