Goolie due for treatment? One’s fixed (9)

I believe the answer is:

ideologue

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'one's fixed' is the definition.
I can't judge whether this defines the answer.

'goolie due for treatment?' is the wordplay.
'for treatment?' is an anagram indicator (the anagram must be processed or treated).
'goolie'+'due'='gooliedue'
'gooliedue' is an anagram of 'IDEOLOGUE'.

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(Other definitions for ideologue that I've seen before include "Dogmatic theorist" , "Dogmatic type" , "Political reactionary" , "Dogmatic sort" , "Dogmatist" .)

I've seen this clue in The Guardian.

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