A surreptitious kiss outside before social activity in an Alpine resort? (5,3)
I believe the answer is:
apres-ski
'social activity in an alpine resort?' is the definition.
'a surreptitious kiss outside before' is the wordplay.
'surreptitious' is an anagram indicator.
'outside' indicates putting letters inside.
'before' becomes 'pre' (**).
'kiss' is an anagram of 'sski'.
'sski' enclosing 'pre' is 'presski'.
'a'+'presski'='APRES-SKI'
(Other definitions for apres-ski that I've seen before include "Winter sports socialising" , "holiday entertainment" , "Alpine jollities" , "socialising in Davos?" , "Alpine holiday fun?" .)