Perform duties for one in church (8)

I believe the answer is:

minister

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'perform duties' is the definition.
I can't tell whether this defines the answer.

'one in church' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'church' becomes 'minster' (minster is a kind of church).
'i' put into 'minster' is 'MINISTER'.

'for' acts as a link.

Can you help me to learn more?

(Other definitions for minister that I've seen before include "Merit sin (anag.)" , "Member of parliament" , "Agent" , "supply as before" , "Member of government or clergy" .)

I've seen this clue in The Globe and Mail.

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