Go with some extra velocity? (6)
I believe the answer is:
travel
'go' is the definition.
(I know that go can be written as travel)
'with some extra velocity?' is the wordplay.
'with' indicates a hidden word.
'TRAVEL' can be found hidden inside 'some extra velocity'.
(Other definitions for travel that I've seen before include "Go on a journey" , "Go on a trip" , "tour" , "Movement from one place to another" , "Locomotion" .)