The most common and most likely answer to this crossword clue is the 9 letter word PEN-NAMES
P
E
N
-
N
A
M
E
S
Buddy explains!
The straight part
We know that "psuedonyms" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case psuedonyms = pen-names.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 PEN-NAMES mean?
PEN-NAMES noun- A fictitious name used by an author in place of their actual name; a writer's pseudonym.