The most common and most likely answer to this crossword clue is the 7 letter word WEASELS
I've seen this crossword clue in Financial Times
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More clues leading to the result WEASELS
Buddy explains!
The straight part
We know that "treasonous people" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case treasonous people = weasels.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 WEASELS mean?
WEASELS noun- The least weasel, Mustela nivalis.
- Any of the carnivorous mammals of the genus Mustela, having a slender body, a long tail and usually a light brown upper coat and light-coloured belly.
- The taxonomic family Mustelidae is also called the weasel family.
- A devious or sneaky person or animal.
- A type of yarn winder used for counting the yardage of handspun yarn. It most commonly has a wooden peg or dowel that pops up from the gearing mechanism after a certain number of yards have been wound onto the winder.
- To achieve by clever or devious means.
- To gain something for oneself by clever or devious means.
- To engage in clever or devious behavior.