First kitty up-ended (3)
I believe the answer is:
top
'first' is the definition.
(top can mean the best or first)
'kitty up-ended' is the wordplay.
'kitty' becomes 'pot' (both can mean a shared fund).
'up-ended' says the letters should be written backwards (in a down clue, letters go up).
'pot' backwards is 'TOP'.
(Other definitions for top that I've seen before include "Toy; uppermost point" , "Upper side" , "SECOND PART OF 10 ACROSS" , "Toy; garment" , "Finest" .)