Answer:

ghostwriter

Answer	Crossword Clue
GHOSTWRITER	Memoirs helper, often
GHOSTWRITER	Uncredited author
GHOSTWRITER	Autobiographer, often

GHOSTWRITER	Author behind the scenes
GHOSTWRITER	Author who gets no credit
GHOSTWRITER	Author's secret collaborator
GHOSTWRITER	Behind-the-scenes author
GHOSTWRITER	Halloween novelist?
GHOSTWRITER	Collaborator of a sort
GHOSTWRITER	Author of a sort.
GHOSTWRITER	Type of author.

GHOSTWRITER	Halloween correspondent?
GHOSTWRITER	Author who'll never make a name for himself
GHOSTWRITER	Many an autobiographer's need
GHOSTWRITER	Sorensen, to Kennedy
GHOSTWRITER	Author of scary stories?
GHOSTWRITER	Secret collaborator
GHOSTWRITER	He or she can't be known