Knockout kiss for a bit of money (6)
I believe the answer is:
kopeck
'bit of money' is the definition.
The answer and definition can be both quantities as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'knockout kiss' is the wordplay.
'knockout' becomes 'ko' (abbreviation).
'kiss' becomes 'peck' (pecking is a kind of kissing).
'ko'+'peck'='KOPECK'
'for a' is the link.
Can you help me to learn more?
(Other definitions for kopeck that I've seen before include "One-hundredth of a rouble" , "One hundred of these make one rouble" , "Russian copper" , "little Russian money" , "Russian coin" .)