Kitty has delightful day (4)
I believe the answer is:
fund
'kitty' is the definition.
(I've seen this before)
'delightful day' is the wordplay.
'delightful' becomes 'fun' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'day' becomes 'd'.
'fun'+'d'='FUND'
'has' acts as a link.
Can you help me to learn more?
(Other definitions for fund that I've seen before include "Monetary resources" , "Finance" , "Supply cash" , "Sponsor" , "Cash reserve" .)