Jack after Oscar competes with leading male actor (5,4)
I believe the answer is:
movie star
'actor' is the definition.
(movie star is a kind of actor)
'jack after oscar competes with leading male' is the wordplay.
I cannot really understand how this works, but
'jack' could be 'tar' (both are informal terms for sailor) and 'tar' is found in the answer.
'oscar' could be 'o' (phonetic alphabet: alpha, bravo, charlie etc.) and 'o' is found within the answer.
'competes' could be 'vies' ('vie' can be a synonym of 'compete') and 'vies' is found within the answer.
'male' could be 'm' (common abbreviation) and 'm' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for movie star that I've seen before include "Big player" , "Film idol" , "VIP on set" , "Cruise, perhaps" , "Hoping for an Oscar" .)