The most common and most likely answer to this crossword clue is the 11 letter word GHOST-WRITE
I've seen this crossword clue in The Times
G
H
O
S
T
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W
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More clues leading to the result GHOST-WRITE
Buddy explains!
The straight part
We know that "Author secretly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case author secretly = ghost-write.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.
What does GHOST-WRITE mean?
GHOST-WRITE verb- (authorship) To write under the name of another (especially literary works).
- (authorship) To author a literary work or speech in the place of another.