One with plans for passing Tesla motorcar, say (7)

I believe the answer is:

testate

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'one with plans' is the definition.
I can't tell whether this defines the answer.

'passing tesla motorcar say' is the wordplay.
'passing tesla motorcar' becomes 'te' (I can't justify this - if you can you should believe this answer much more).
'say' becomes 'state' (synonyms).
'te'+'state'='TESTATE'

'for' acts as a link.

Can you help me to learn more?

(Other definitions for testate that I've seen before include "State of having made a will" , "Having written a valid will" , "Leaving a will" , "Having left valid will at death" , "Having left a legacy" .)

I've seen this clue in The Guardian.

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