The most common and most likely answer to this crossword clue is the 14 letter word CONSPIRATORIAL
I've seen this crossword clue in Independent
C
O
N
S
P
I
R
A
T
O
R
I
A
L
More clues leading to the result CONSPIRATORIAL
Buddy explains!
The straight part
We know that "plotting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plotting = conspiratorial.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 CONSPIRATORIAL mean?
CONSPIRATORIAL adjective- Pertaining to conspiracy or conspirators.