'Smack' in Greek is 'skampili' (4)
I believe the answer is:
kiss
'smack' is the definition.
(smack can informally mean a kiss)
'in greek is skampili' is the wordplay.
'in' indicates the answer is hidden within the clue.
'KISS' can be found hidden inside 'greek is skampili'.
(Other definitions for kiss that I've seen before include "Expression of love" , "Smack; peck" , "Act of osculation" , "Cross" , "Neck - peck" .)