The most common and most likely answer to this crossword clue is the 6 plus 9 letter word ERNEST HEMINGWAY
I've seen this crossword clue in The Guardian
E
R
N
E
S
T
H
E
M
I
N
G
W
A
Y
More clues leading to the result ERNEST HEMINGWAY
- American author conjuring up new nightmare, yes?
- Novelist’s grave edging, reportedly, covers passage
- Ambassador in West Germany in novel – author?
- Writer has eagle on rock encapsulating the dynasty
- In West Germany, he got drunk
- Author, when wild with enmity, rages
- Ambassador in West Germany in novel - author?
- Birds of prey a mighty new development for this writer
- American writer in West Germany, he travels
Buddy explains!
The straight part
We know that "American author" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case american author = ernest hemingway.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.