Ridiculously early race (5)
I believe the answer is:
relay
'race' is the definition.
(relay race)
'ridiculously early' is the wordplay.
'ridiculously' indicates an anagram (I've seen this in other clues).
'early' is an anagram of 'RELAY'.
(Other definitions for relay that I've seen before include "Hand, pass on" , "Receive and pass on - race" , "Team of workers" , "supplementary store of anything" , "track event" .)