Uses energy in remote region (6)
I believe the answer is:
wields
'uses' is the definition.
('wield' can be a synonym of 'use')
'energy in remote region' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'in' indicates putting letters inside.
'remote region' becomes 'wilds'.
'e' put inside 'wilds' is 'WIELDS'.
(Other definitions for wields that I've seen before include "Holds and brandishes, say a weapon" , "Exercises (power)" , "Holds and uses, say weapon, with the hands" .)