The most common and most likely answer to this crossword clue is the 9 plus 5 letter word ALEXANDRE DUMAS
I've seen this crossword clue in The Daily Telegraph
A
L
E
X
A
N
D
R
E
D
U
M
A
S
More clues leading to the result ALEXANDRE DUMAS
Buddy explains!

The straight part
We know that "Author" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case author = alexandre dumas.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.