Mark concealing a bird inside vehicle (6,3)

I believe the answer is:

saloon car

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'vehicle' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's a link between them I don't understand?

'mark concealing a bird' is the wordplay.
'mark' becomes 'scar' (mark left by an injury).
'concealing' is an insertion indicator.
'bird' becomes 'loon' (loon is a kind of bird).
'a'+'loon'='aloon'
'scar' placed around 'aloon' is 'SALOON-CAR'.

'inside' acts as a link.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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