Kitty requiring some of the stuff underneath (4)
I believe the answer is:
fund
'kitty' is the definition.
(fund or money for a particular purpose)
'some of the stuff underneath' is the wordplay.
'some of' says the answer is hidden in the clue.
'FUND' can be found hidden inside 'stuff underneath'.
'requiring' is the link.
(Other definitions for fund that I've seen before include "Sponsor" , "Provide with money, say project" , "Give money" , "Cash reserve" , "Finance" .)