I make good, to some extent (3)
I believe the answer is:
ego
'i' is the definition.
(thesaurus)
'make good to some extent' is the wordplay.
'to some extent' says the answer is hidden in the clue.
'EGO' can be found hidden inside 'make good'.
(Other definitions for ego that I've seen before include "Personal pride" , "Self-confidence" , "One's self-image" , "One's image of oneself" , "In Virgil I" .)