With inner energy not ace, fictional hero just about manages (4,2)
I believe the answer is:
gets by
'manages' is the definition.
('get by' can be a synonym of 'manage')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for gets by that I've seen before include "Planet Herschel found" , "Manages" , "makes do" , "copes" .)