The most common and most likely answer to this crossword clue is the 9 letter word AGITATORS
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Buddy explains!

The straight part
We know that "political activists" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case political activists = agitators.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 AGITATORS mean?
AGITATORS noun- One who agitates; one who stirs up or excites others, for example political reformers.
- An implement for shaking or mixing.
- One of a body of men appointed by the army, in Cromwell's time, to look after their interests; called also adjutators.