Indy 500 competitor (5)
I believe the answer is:
'indy 500 competitor' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for racer that I've seen before include "Bike, perhaps" , "one in a hurry" , "American snake" , "Speedway competitor, perhaps" , "Fast-moving animal" .)