Exceptional talent of Bill in race, swimming (10)
I believe the answer is:
brilliance
'exceptional talent' is the definition.
(brilliant can mean very talented)
'bill in race swimming' is the wordplay.
'swimming' indicates anagramming the letters.
'bill'+'in'+'race'='billinrace'
'billinrace' with letters rearranged gives 'BRILLIANCE'.
'of' is the link.
(Other definitions for brilliance that I've seen before include "Brightness, vividness" , "Brightness; cleverness" , "Genius; brightness" , "Exceptional cleverness" , "Sparkling aptitude" .)