Fast car (5)
'fast car' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for speedster that I've seen before include "Fast car (or driver)" , "He's Fleet" , "sports car" .)
'fast car' is the definition.
(race car)
This is all the clue.
(Other definitions for racer that I've seen before include "Participant in speed contest" , "Bike, perhaps" , "Fast-moving animal" , "one in a hurry" , "Run competitor; snake" .)