Purchase motor for old vehicle (8,6)

I believe the answer is:

traction engine

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'old vehicle' is the definition.
'traction engine' can be an answer for 'vehicle' (traction engine is a kind of vehicle). I am unsure of the 'old' bit.

'purchase motor' is the wordplay.
'purchase' becomes 'traction' (as in grip on a surface).
'motor' becomes 'engine' (engine is a kind of motor).
'traction'+'engine'='TRACTION-ENGINE'

'for' acts as a link.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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