The most common and most likely answer to this crossword clue is the 5 plus 10 letter word BERYL BAINBRIDGE
I've seen this crossword clue in The Guardian
B
E
R
Y
L
B
A
I
N
B
R
I
D
G
E
Buddy explains!
The straight part
We know that "Writer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case writer = beryl bainbridge.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.