Astuteness of a copper with labourers (6)
I believe the answer is:
acumen
'astuteness' is the definition.
(I know that acumen is a type of astuteness)
'a copper with labourers' is the wordplay.
'copper' becomes 'cu' (chemical symbol).
'with' is a charade indicator (letters next to each other).
'labourers' becomes 'men' (I can't justify this - if you can you should believe this answer much more).
'a'+'cu'+'men'='ACUMEN'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for acumen that I've seen before include "intuition" , "Sharpness, penetration, quickness of perception" , "Ability to judge quickly and well" , "Kind of sagacity, good for business" , "Astuteness, penetration" .)