Nothing winning about kiss, a second indiscretion (4,3)
I believe the answer is:
faux pas
'a second indiscretion' is the definition.
'faux pas' can be an answer for 'indiscretion' (a faux pas is a mistake or indiscretion). I am unsure of the 'a second' bit.
'nothing winning about kiss' is the wordplay.
'nothing' becomes 'fa' (slang term - sweet Fanny Adams).
'winning' becomes 'upas' (I can't explain this - if you can you should believe this answer much more).
'about' is an insertion indicator.
'kiss' becomes 'x' (X can represent a kiss).
'upas' placed around 'x' is 'uxpas'.
'fa'+'uxpas'='FAUX-PAS'
(Other definitions for faux pas that I've seen before include "Socially tactless act" , "Social error" , "Bloomer" , "Social gaffe" , "Embarrassing blunder" .)