Worried as nine go mad (6)

I believe the answer is:

insane

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'mad' is the definition.
(I know that mad can be written as insane)

'worried as nine' is the wordplay.
'worried' indicates an anagram.
'as'+'nine'='asnine'
'asnine' anagrammed gives 'INSANE'.

'go' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for insane that I've seen before include "nuts" , "off trolley" , "Sienna (anag.)" , "Anne is (anag) - crazy" , "out to lunch" .)

I've seen this clue in The Mirror.

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