Dire actor in cast fixated with theory (11)

I believe the answer is:

doctrinaire

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'fixated with theory' is the definition.
I can't judge whether this definition defines the answer.

'dire actor in cast' is the wordplay.
'cast' is an anagram indicator (letters are dispersed or cast around).
'dire'+'actor'+'in'='direactorin'
'direactorin' with letters rearranged gives 'DOCTRINAIRE'.

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(Other definitions for doctrinaire that I've seen before include "Inflexible in applying theory" , "not practical" , "Trying to impose beliefs" , "Inclined to follow principles to unworkable extremes" , "Dogmatic" .)

I've seen this clue in The Independent.

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