Document parasites in first Norman church (7)

I believe the answer is:

licence

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'document' is the definition.
(I know that licence is a type of instrument)

'parasites in first norman church' is the wordplay.
'parasites in' becomes 'lice' (I can't explain this - if you can you should believe this answer much more).
'first norman' becomes 'n' (lst letter of 'norman').
'church' becomes 'CE' (abbreviation for Church of England).
'lice'+'n'+'ce'='LICENCE'

Can you help me to learn more?

(Other definitions for licence that I've seen before include "Self-indulgence; permit" , "the green light" , "Permit - freedom" , "Official autorisation" , "Freedom of action" .)

I've seen this clue in The Mirror.

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