The most common and most likely answer to this crossword clue is the 9 letter word DOOMSAYER
D
O
O
M
S
A
Y
E
R
More clues leading to the result DOOMSAYER
Buddy explains!
The straight part
We know that "Pessimist" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pessimist = doomsayer.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 DOOMSAYER mean?
DOOMSAYER noun- One who makes dire predictions about the future; one who predicts doom.