Kitty having enjoyable day (4)
I believe the answer is:
fund
'kitty' is the definition.
(fund or money for a particular purpose)
'enjoyable day' is the wordplay.
'enjoyable' becomes 'fun' (fun means enjoyable or pleasing).
'day' becomes 'd' (abbreviation for day).
'fun'+'d'='FUND'
'having' is the link.
(Other definitions for fund that I've seen before include "Monetary resources" , "Sponsor" , "Reserve of money for future use" , "Cash reserve" , "Pool of money" .)