The most common and most likely answer to this crossword clue is the 10 letter word PRETENDERS
I've seen this crossword clue in Independent
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Buddy explains!
The straight part
We know that "Charles Edward Stuart and Perkin Warbeck?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case charles edward stuart and perkin warbeck? = pretenders.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 PRETENDERS mean?
PRETENDERS noun- A person who professes beliefs and opinions that they do not hold.
- A claimant to an abolished or already occupied throne.