Fabled racer (4)
I believe the answer is:
hare
'fabled racer' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for hare that I've seen before include "Long-eared mammal" , "Herbivore" , "Swift mammal" , "Timid creature" , "Rabbit-like animal" .)