Train? Yes and no (5)

I believe the answer is:

coach

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'train?' is the definition.
(I know that train can be written as coach)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for coach that I've seen before include "Trainer - vehicle" , "Trainer as of soccer team" , "Type of bus" , "Vehicle; instructor" , "Train - or part of one!" .)

I've seen this clue in the Evening Standard.

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