Competitor in an event ran terribly (7)
I believe the answer is:
entrant
'competitor' is the definition.
(someone who has entered a competition)
'in an event ran terribly' is the wordplay.
'in' says the answer is hidden in the clue.
'ENTRANT' is hidden within 'event ran terribly'.
(Other definitions for entrant that I've seen before include "Someone signing up for a competition" , "New participant" , "Candidate" , "Someone coming in" , "Contestant; starter" .)