Macabre writer, or the first three letters of his occupation (3)
I believe the answer is:
poe
(Other definitions for poe that I've seen before include "Edgar Allan ..., American writer of the macabre" , "The Raven writer" , "Entrance rooms; seeks support from" , "Edgar Allan . . ., American writer of horror stories" , "Author of The Murders in the Rue Morgue" .)