Continue in the same line and race ahead (3,2)
I believe the answer is:
run on
'continue in the same line' is the definition.
(printing term)
'race ahead' is the wordplay.
'race' becomes 'run' ('run' can be a synonym of 'race').
'ahead' becomes 'on' ('on' can be a synonym of 'ahead'**).
'run'+'on'='RUN-ON'
'and' acts as a link.
(Other definitions for run on that I've seen before include "Keep talking" , "Talk continuously" , "Go past the normal finishing time" , "continue without interruption" .)