The most common and most likely answer to this crossword clue is the 9 letter word FLOWERBED
I've seen this crossword clue in The Times
F
L
O
W
E
R
B
E
D
Buddy explains!
The straight part
We know that "the plot of The Black Tulip" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the plot of the black tulip = flowerbed.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 FLOWERBED mean?
FLOWERBED noun- A part of a garden or park where flowers are grown.