Competitor in event ran twice (7)
I believe the answer is:
entrant
'competitor' is the definition.
(someone who has entered a competition)
'in event ran twice' is the wordplay.
'in' says the answer is hidden in the clue.
'ENTRANT' can be found hidden inside 'event ran twice'.
(Other definitions for entrant that I've seen before include "Contestant; starter" , "One going in for exam" , "Participant in, eg, a race" , "Competitor, contestant" , "One going in for a race or competition" .)