Self-confidence of English advance (3)
I believe the answer is:
ego
'self-confidence' is the definition.
(I've seen this in another clue)
'english advance' is the wordplay.
'english' becomes 'e' (abbreviation).
'advance' becomes 'go' (to advance is to go forward).
'e'+'go'='EGO'
'of' is the link.
(Other definitions for ego that I've seen before include "Sense of identity" , "Self-esteem or self-importance" , "Aspect of the personality" , "One's self image" , "Morale" .)