Four-legged race (5)
I believe the answer is:
relay
'race' is the definition.
(relay race)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for relay that I've seen before include "Team of workers" , "Receive and pass on - race" , "track event" , "Hand, pass on" , "Pass on - put down again" .)