Monk's office, earlier his extraordinary source of power (9)

I believe the answer is:

priorship

'monk's office' is the definition.

'earlier his extraordinary source of power' is the wordplay.
'earlier' becomes 'prior' ('prior' can be a synonym of 'earlier'**).
'extraordinary' is an anagram indicator.
'source of' suggests taking the first letters.
The initial letter of 'power' is 'p'.
'his' with letters rearranged gives 'shi'.
'prior'+'shi'+'p'='PRIORSHIP'

(Another definition for priorship that I've seen is " Religious office".)

I've seen this clue in The Times.

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