Inspectors dismiss returning pit workers (9)
I believe the answer is:
examiners
'inspectors' is the definition.
('examiner' can be a synonym of 'inspector')
'dismiss returning pit workers' is the wordplay.
'dismiss' becomes 'axe' (I've seen this before).
'returning' says the letters should be written backwards.
'pit workers' becomes 'miners' (people working down in a pit).
'axe' back-to-front is 'exa'.
'exa'+'miners'='EXAMINERS'
(Other definitions for examiners that I've seen before include "Inspectors" , "Testers" .)