Cat in pool (5)
I believe the answer is:
kitty
I believe this is a double definition.
'cat' is the first definition.
(informal term for a cat)
'pool' is the second definition.
(both can mean a shared fund)
'in' acts as a link.
(Other definitions for kitty that I've seen before include "Perhaps a small Abyssinian" , "Pool - 4 down" , "Young domestic pet" , "Pool of bets in gambling" , "19 - diminutive name for girl or pet" .)