The most common and most likely answer to this crossword clue is the 8 letter word USURPERS
I've seen this crossword clue in The Daily Telegraph
U
S
U
R
P
E
R
S
More clues leading to the result USURPERS
Buddy explains!
The straight part
We know that "those seizing power" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case those seizing power = usurpers.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 USURPERS mean?
USURPERS noun- One who usurps.