Workers supporting a copper's insight (6)
I believe the answer is:
acumen
'insight' is the definition.
(I've seen this before)
'workers supporting a copper's' is the wordplay.
'workers' becomes 'men' (men can mean staff or employees).
'supporting' says to put letters next to each other (in a down clue, some letters go below others).
'copper' becomes 'Cu' (chemical symbol).
'a'+'cu'='acu'
'men' put after 'acu' is 'ACUMEN'.
(Other definitions for acumen that I've seen before include "Penetrating insight" , "show perception" , "Shrewdness, intelligence in business" , "Discernment - insight" , "Cleverness in business" .)