Evil giants worried local guards (10)

I believe the answer is:

vigilantes

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'local guards' is the definition.
The definition and answer can be both people as well as being plural nouns.
Perhaps there's an association between them I don't understand?

'evil giants worried' is the wordplay.
'worried' indicates anagramming the letters (worry can mean to interfere with or disturb).
'evil'+'giants'='evilgiants'
'evilgiants' with letters rearranged gives 'VIGILANTES'.

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I've seen this clue in The Irish Times.

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