Kitty changed top (3)
I believe the answer is:
pot
'kitty' is the definition.
(I've seen this before)
'changed top' is the wordplay.
'changed' indicates anagramming the letters.
'top' with letters rearranged gives 'POT'.
(Other definitions for pot that I've seen before include "Preserve; drug" , "Trophy; kitty" , "Weed" , "Cooking vessel, plant container and street drug" , "Container for 23" .)