Way to get a kitty cat plump (4-5)
I believe the answer is:
whip-round
'way to get a kitty' is the definition.
(a whip-round might create a fund or kitty)
'cat plump' is the wordplay.
'cat' becomes 'whip' (cat o' nine tails or cat is a type of whip).
'plump' becomes 'round' (plump can mean round or full).
'whip'+'round'='WHIP-ROUND'
(Other definitions for whip-round that I've seen before include "Collection of money as in office" , "Quick collection of cash contributions" , "Collection of money from members of group" , "Impromptu collection of money" , "An office collection as for someone retiring" .)