Answer:

dearjohn

Answer	Crossword Clue
DEARJOHN	Foreboding salutation
DEARJOHN	A letter you don't want to receive
DEARJOHN	Letter bomb?

DEARJOHN	Last letter?
DEARJOHN	Letter of a kind.
DEARJOHN	Certain kind of letter
DEARJOHN	Letter of regret to a G.I.
DEARJOHN	Beginning of the end of a relationship?
DEARJOHN	Prelude to a breakup
DEARJOHN	Start of a split?