Vehicles for second class road purposes (5)

I believe the answer is:

buses

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'vehicles' is the definition.
(bus is a kind of vehicle)

'second class road purposes' is the wordplay.
'second class' becomes 'b'.
'road purposes' becomes 'uses' ('use' can be a synonym of 'purpose'. I am not sure about the 'road' bit.).
'b'+'uses'='BUSES'

'for' acts as a link.

Can you help me to learn more?

(Other definitions for buses that I've seen before include "Public transport vehicles" , "Public service vehicles" , "Passenger vehicles" .)

I've seen this clue in the Evening Standard.

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