I leave after end of June (3)
I believe the answer is:
ego
'i' is the definition.
('I' in Latin)
'leave after end of june' is the wordplay.
'leave' becomes 'go' (to go is to depart or leave).
'after' is a charade indicator (letters next to each other).
'end of' indicates one should take the final letters.
The last letter of 'june' is 'e'.
'go' put after 'e' is 'EGO'.
(Other definitions for ego that I've seen before include "(Person's) sense of self-esteem" , "Vowel to disappear, < say another" , "In Virgil I" , "One's self image" , "Part of the mind" .)