Baton-passing event (5)
'baton-passing event' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for relay race that I've seen before include "Event in which a baton is passed" , "Baton-passing event?" , "Ace rarely placed in team event" , "having started, one couldn't finish it" , "Team contest" .)
(Other definitions for relay that I've seen before include "Team of workers" , "Hand, pass on" , "Pass on - put down again" , "article in bank" , "Broadcast" .)