Clue: Frank Sinatra's heart broken, nation supporting Martin initially (3-2-3)
Answer: MAN-TO-MAN
Explanation: Frank Sinatra's heart broken, nation supporting Martin initially (3-2-3)
*(nat) (the heart of "Si**NAT**ra") + **OMAN **("nation") "supporting" **M**(artin), so **M****(ANT)OMAN