Urges on (6)
I believe the answer is:
impels
'urges on' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for impels that I've seen before include "Drives or forces" , "Spurs" , "Drives on in simple way" , "Urges or drives to do something" , "Urges forward" .)