Dash off with runner politician (5)
I believe the answer is:
skimp
'dash off' is the definition.
(both can mean to do something carelessly)
'with runner politician' is the wordplay.
'with' means one lot of letters go next to another.
'runner' becomes 'ski' (something which 'runs', ie moves quickly on snow).
'politician' becomes 'MP' (Member of Parliament).
'ski' next to 'mp' is 'SKIMP'.
(Other definitions for skimp that I've seen before include "save" , "Stint, scrimp" , "Spend not enough time and care on (job)" , "Withhold" , "Be niggardly" .)