Shrewdness (6)
'shrewdness' is the definition.
(acumen can mean shrewdness or good judgment)
This is the entire clue.
(Other definitions for acumen that I've seen before include "Shrewdness, intelligence in business" , "Shrewdness, good for business" , "Business sense" , "Gumption" , "ability to make good judgements" .)
'shrewdness' is the definition.
(I know that shrewdness can be written as astuteness)
This is all the clue.
(Other definitions for astuteness that I've seen before include "Penetration" , "Canny" , "Shrewdness" , "perception" , "Sagacity" .)