Kitty's play date (4)
I believe the answer is:
fund
'kitty's' is the definition.
(fund or money for a particular purpose)
'play date' is the wordplay.
'play' becomes 'fun' (synonyms).
'date' becomes 'd' (common abbreviation eg in DOB, date of birth).
'fun'+'d'='FUND'
(Other definitions for fund that I've seen before include "Supply cash" , "Provide with money, say project" , "Pay for; kitty" , "Stock, resources" , "Reserve of money for future use" .)