They attack stains, alas, in an ill-advised way (10)

I believe the answer is:

assailants

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'they' is the definition.
Both the answer and definition are plural nouns.
Maybe you can see a link between them that I don't see?

'attack stains alas in an ill-advised way' is the wordplay.
'stains alas' can be anagrammed to 'ASSAILANTS'.
But, I am not clear how the anagram is indicated.

Can you help me to learn more?

I've seen this clue in The Irish Times.

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