They check papers of old pitmen around area (9)

I believe the answer is:

examiners

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'they check papers' is the definition.
The definition suggests an adverb but the answer is not.

'old pitmen around area' is the wordplay.
'old' becomes 'ex'.
'pitmen' becomes 'amirs' (I can't justify this - if you can you should give a lot more credence to this answer).
'around' means one lot of letters goes inside another.
'area' becomes 'ne'.
'amirs' placed around 'ne' is 'aminers'.
'ex'+'aminers'='EXAMINERS'

'of' acts as a link.

Can you help me to learn more?

(Other definitions for examiners that I've seen before include "Inspectors" , "Testers" .)

I've seen this clue in The Independent.

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