Successful register entry? (2,1,4)
I believe the answer is:
on a roll
'successful' is the definition.
'register entry?' is the wordplay.
I cannot really see how this works, but
'register' could be 'roll' (list of names) and 'roll' is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for on a roll that I've seen before include "Having long spell of good luck" , "Where one may find sesame seeds" , "name could be found here?" , "keeps having repeated wins" , "Enjoying a winning streak" .)