Winning steadily (2,1,4)
I believe the answer is:
on a roll
'winning steadily' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for on a roll that I've seen before include "Going through a good patch" , "enjoying lots of success" , "thus far unbeaten competitor?" , "Where one may find sesame seeds" , "How butter may be spread" .)