The most common and most likely answer to this crossword clue is the 11 letter word CONSPIRATOR
I've seen this crossword clue in The Daily Telegraph
C
O
N
S
P
I
R
A
T
O
R
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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 CONSPIRATOR mean?
CONSPIRATOR noun- One of a group that acts in harmony; a person who is part of a conspiracy.
- Part of a group that agree to do an unlawful or unethical act.