There are spare ones in plenty, reserved (5)

I believe the answer is:

tyres

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'there are spare ones' is the definition.
I can't tell whether this defines the answer.

'in plenty reserved' is the wordplay.
'in' indicates a hidden word.
'TYRES' can be found hidden inside 'plenty reserved'.

Can you help me to learn more?

(Other definitions for tyres that I've seen before include "Rubber wheel covers" , "rubber rings" , "Wheel coverings" , "Wheel hoops" .)

I've seen this clue in the Evening Standard.

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