Leave; off you go (3,5)
I believe the answer is:
run along
I believe this is a double definition.
'leave' is the first definition.
(thesaurus)
'off you go' is the second definition.
(I've seen this before)
(Other definitions for run along that I've seen before include "Imperative for leaving" , "Go away!" , "Informally leave or depart - on the trot?" .)