Debar unionist actively refusing to submit to authority (13)

I believe the answer is:

insubordinate

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'submit to authority' is the definition.
I can't tell whether this defines the answer.

'debar unionist actively refusing' is the wordplay.
'debar unionist' anagrams to 'INSUBORDINATE'.
Though, I am not clear how the anagram is indicated.

'to' is the link.

Can you help me to learn more?

(Other definitions for insubordinate that I've seen before include "Rebellious" , "Mutinous" , "Disobedient" , "undisciplined" , "Defiant of authority" .)

I've seen this clue in The Times.

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