Judgement of people supporting a copper (6)
I believe the answer is:
acumen
'judgement' is the definition.
(thesaurus)
'people supporting a copper' is the wordplay.
'people' becomes 'men' (men are people).
'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'.
'of' is the link.
(Other definitions for acumen that I've seen before include "Sagicity as in business" , "Quick intelligence" , "Ability to judge and decide quickly" , "Keen intelligence" , "Keen perception" .)