Where I might put butter, having great success (2,1,4)
I believe the answer is:
on a roll
I believe this clue is a double definition.
'where i might put butter' is the first definition.
(you might spread butter on a bread roll)
'having great success' is the second definition.
(someone on a roll is having great success)
(Other definitions for on a roll that I've seen before include "Having long spell of good luck" , "enjoying lots of success" , "name could be found here?" , "Having a run of success" , "continually successful" .)