Cairns had freaky spiders (9)

I believe the answer is:

arachnids

I'm a little stuck... Click here to teach me more about this clue!

'freaky spiders' is the definition.
The definition and answer can be both animals as well as being plural nouns.
Maybe you can see an association between them that I can't see?

'cairns had' is the wordplay.
'cairns had' anagrams to 'ARACHNIDS'.
Though, I am unsure how the anagram is indicated.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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