Power drive (6)
I believe the answer is:
energy
I believe this is a double definition.
'power' is the first definition.
('energy' can be a synonym of 'power')
'drive' is the second definition.
(energy is a kind of drive)
(Other definitions for energy that I've seen before include "Vigour, animation" , "Zest" , "Capacity for action" , "Go green, possibly with envy, ultimately" , "Power - drive" .)