Shrewdness of top don finally taking in university (6)
I believe the answer is:
acumen
'shrewdness' is the definition.
(acumen is a kind of shrewdness)
'top don finally taking in university' is the wordplay.
'top' becomes 'acme' ('acme' can be a synonym of 'top'**).
'finally' suggests the final letters.
'taking in' is an insertion indicator.
'university' becomes 'u'.
The final letter of 'don' is 'n'.
'acme'+'n'='acmen'
'acmen' enclosing 'u' is 'ACUMEN'.
'of' acts as a link.
(Other definitions for acumen that I've seen before include "ingenuity" , "'Shrewdness, in business perhaps (6)'" , "Penetrating insight" , "Ability to take well judged decisions" , "Keen insight, shrewdness" .)