Motor sport made the grade when vehicle reversed in (4,4)

I believe the answer is:

drag race

I'm a little stuck... Click here to teach me more about this clue!

'motor sport' is the definition.
(I know that drag race is a type of motor sport)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for drag race that I've seen before include "motor sport contest" , "Contest of car acceleration" , "Short car event to test acceleration" , "Fast track career" , "competitive drive" .)

I've seen this clue in the Sydney Morning Herald.

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