Competitor in event ran tactically (7)
I believe the answer is:
entrant
'competitor' is the definition.
(someone who has entered a competition)
'in event ran tactically' is the wordplay.
'in' says the answer is hidden in the clue.
'ENTRANT' can be found hidden inside 'event ran tactically'.
(Other definitions for entrant that I've seen before include "One taking part in a race or competition" , "One going in for a race or competition" , "Someone taking part in a competition" , "Competitor, contestant" , "Who goes in" .)