Feel bad about entering to damage post vehicle (4,3)

I believe the answer is:

mail car

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'post vehicle' is the definition.
'mail car' can be an answer for 'vehicle' (mail car is a kind of vehicle). I am not sure about the 'post' bit.

'feel bad about entering to damage' is the wordplay.
'feel bad' becomes 'ail' (I've seen this in another clue).
'about' becomes 'c' (abbreviation for 'circa').
'entering' is an insertion indicator.
'to damage' becomes 'mar' (to mar is to spoil or damage).
'ail'+'c'='ailc'
'ailc' inserted into 'mar' is 'MAIL CAR'.

Can you help me to learn more?

I've seen this clue in The Independent.

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