Had consumed one dry sandwich to get going (3,3,4)
I believe the answer is:
hit the road
'get going' is the definition.
'had consumed one dry sandwich' is the wordplay.
'consumed' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'dry' becomes 'tt' (abbreviation for teetotal).
'sandwich' becomes 'hero' (hero is a kind of sandwich**).
'i'+'tt'+'hero'='itthero'
'had' placed around 'itthero' is 'HIT THE ROAD'.
'to' acts as a link.
(Other definitions for hit the road that I've seen before include "go" , "Leave (slang)" .)