Kiss male when in celebration (4)
I believe the answer is:
xmas
'celebration' is the definition.
(I know that Xmas is a Christian holy day)
'kiss male when' is the wordplay.
'kiss' becomes 'x' (X can represent a kiss).
'male' becomes 'm' (common abbreviation).
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'x'+'m'+'as'='XMAS'
'in' acts as a link.
(Other definitions for xmas that I've seen before include "annual holiday" , "Yule, Noel" , "Abbreviation for a winter festival" , "Short celebration" , "Christmas (abbrev.)" .)