A media king half ignored this social activity (5-3)
I believe the answer is:
apres-ski
'this social activity' is the definition.
(apres-ski is socialising after skiing)
'a media king half ignored' is the wordplay.
'media' becomes 'press' (the press is part of the media).
'half ignored' suggests halving the letters.
'king' halved is 'ki'.
'a'+'press'+'ki'='APRES-SKI'
(Other definitions for apres-ski that I've seen before include "Alpine jollities" , "Nightlife after going on the piste" , "Events after a day on the slopes" , "holiday entertainment" , "Socialising after winter sport" .)