Vicar left rear of vicarage catching what bus? (7)

I believe the answer is:

vehicle

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

I don't understand the rest of the clue.

(Other definitions for vehicle that I've seen before include "4 x 4" , "Eg, car" , "Medium" , "Conveyance for transporting passengers or goods" , "wheels" .)

I've seen this clue in The Sunday Times and The Times.

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