Expecting Jo to leave me too! (2,3,4)
I believe the answer is:
in the club
'expecting' is the definition.
(both can mean pregnant)
'jo to leave me too' is the wordplay.
'to leave' suggests deleting specific letters.
'me too' becomes 'join the club' ('join the club!' means 'me too!').
'jointheclub' with 'jo' removed is 'IN THE CLUB'.
(Other definitions for in the club that I've seen before include "Expecting" , "Possibly accepted" , "Pregnant (slang)" , "not to have been blackballed?" , "putting on weight?" .)