Step aboard to go places (3,2)
I believe the answer is:
get on
This clue is a double definition.
'step aboard' is the first definition.
(I've seen this in another clue)
'go places' is the second definition.
(thesaurus)
'to' acts as a link.
(Other definitions for get on that I've seen before include "fare" , "Make progress, do well in life" , "Make progress or climb aboard" , "Proceed; prosper" , "Obtain promotion" .)