Brewed treacle that goes into superb snowball (10)
I believe the answer is:
accelerate
'snowball' is the definition.
(I've seen this before)
'brewed treacle that goes into superb' is the wordplay.
'brewed' indicates anagramming the letters.
'that goes into' means one lot of letters goes inside another.
'superb' becomes 'ace' (ace can informally mean very good).
'treacle' with letters rearranged gives 'celerat'.
'celerat' placed inside 'ace' is 'ACCELERATE'.
(Other definitions for accelerate that I've seen before include "Increase speed" , "snowball" , "Quicken" , "Crank up" , "Go faster" .)