Inspector formerly a collier (8)

I believe the answer is:

examiner

'inspector' is the definition.
(I know that inspector can be written as examiner)

'formerly a collier' is the wordplay.
'formerly' becomes 'ex' (prefix meaning former or onetime).
'collier' becomes 'miner' (I've seen this in another clue).
'ex'+'a'+'miner'='EXAMINER'

(Other definitions for examiner that I've seen before include "One setting a formal test" , "Tester of knowledge" , "He gives you paper" , "One administering test" , "bloke who will make inspection" .)

I've seen this clue in The Telegraph, The Sun, the Financial Times, The Mirror and The Guardian.

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