No heart gets broken by someone else (7)
I believe the answer is:
'someone else' is the definition.
(I've seen this before)
'no heart gets broken' is the wordplay.
'gets broken' is an anagram indicator.
'noheart' with letters rearranged gives 'ANOTHER'.
'by' is the link.
(Other definitions for another that I've seen before include "Someone else" , "A different one" , "Player or person not yet named or selected" , "A different (thing)" , "A further (item)" .)