The most common and most likely answer to this crossword clue is the 9 letter word PARTISANS
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The straight part
We know that "Supporters" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case supporters = partisans.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 PARTISANS mean?
PARTISANS noun- An adherent to a party or faction.
- A fervent, sometimes militant, supporter or proponent of a party, cause, faction, person, or idea.
- A member of a band of detached light, irregular troops acting behind occupying enemy lines in the ways of harassment or sabotage; a guerrilla fighter.
- The commander of a body of detached light troops engaged in making forays and harassing an enemy.
- A long-handled spear with a triangular, double-edged blade having lateral projections, in some forms also used in boar hunting.
- A soldier armed with such a weapon.