Not the same heart, no different! (7)
I believe the answer is:
another
'not the same' is the definition.
(I've seen this before)
'heart no different' is the wordplay.
'different' is an anagram indicator (letters placed in a different order).
'heart'+'no'='heartno'
'heartno' is an anagram of 'ANOTHER'.
(Other definitions for another that I've seen before include "second" , "No heart (anag.)" , "Additional: alternative" , "Someone else" , "On earth (anag.)" .)