"You and me both" (4,3,4)
(Other definitions for same that I've seen before include "Ditto" , "Aforesaid" , "uniform" , "Identical or similar" , "Identical, unchanged" .)
(Other definitions for ditto that I've seen before include "Two dots indicating the same again" , "Repeat the word(s) above" , "Two small marks indicating the same again" , "As given above" , "As per previous" .)
'you and me both' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for join the club that I've seen before include "Girl's pregnant" , "We're both in that difficult situation!" , "Things are just as bad for me!" , "I have just the same problem!" , "What you do if you sign for United" .)