Energy, ambition (5)
I believe the answer is:
drive
I believe this is a double definition.
'energy' is the first definition.
(I've seen this in another clue)
'ambition' is the second definition.
(I've seen this before)
(Other definitions for drive that I've seen before include "Strong motivation, ambition" , "Propel; outing" , "Hit ball with force" , "Be in charge of car in motion" , "computer store" .)