Filed a fiat, unfortunately, to be brought into association (10)

I believe the answer is:

affiliated

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'be brought into association' is the definition.
I can't judge whether this defines the answer.

'filed a fiat unfortunately' is the wordplay.
'unfortunately' indicates anagramming the letters (a bad or unfortunate spelling).
'filed'+'a'+'fiat'='filedafiat'
'filedafiat' is an anagram of 'AFFILIATED'.

'to' is the link.

Can you help me to learn more?

(Other definitions for affiliated that I've seen before include "adopted" , "in partnership" .)

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

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