Testing parking shelter (8)

I believe the answer is:

proofing

'testing' is the definition.

'parking shelter' is the wordplay.
'parking' becomes 'p' (abbreviation on road signs).
'shelter' becomes 'roofing'.
'p'+'roofing'='PROOFING'

(Another definition for proofing that I've seen is " Making impermeable to water".)

I've seen this clue in The Guardian.

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