Testers set up cutting tool with pit workers (9)
I believe the answer is:
examiners
'testers' is the definition.
(people who test or examine students)
'set up cutting tool with pit workers' is the wordplay.
'set up' is a reversal indicator (in a down clue, letters go up).
'cutting tool' becomes 'axe' (axe is a kind of cutting tool).
'with' says to put letters next to each other.
'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" .)