Energy doubled self-confidence (3)

I believe the answer is:
ego
'self-confidence' is the definition.
(I've seen this before)
'energy doubled' is the wordplay.
I cannot really understand how this works, but
'energy' could be 'go' (go can mean energy or enthusiasm) and 'go' is located in the answer.
A single letter 'e' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ego that I've seen before include "Self-esteem, sense of self" , "Inner self" , "Sense of self, conceit" , "Conscious self" , "Selfishness" .)
