Sporting student to take on uxoricide (9)
I believe the answer is:
bluebeard
'uxoricide' is the definition.
(an uxoricide is a man who kills his wife)
'sporting student to take on' is the wordplay.
'sporting student' becomes 'blue' (sportsperson representing Oxford or Cambridge).
'to' is a charade indicator (letters next to each other).
'take on' becomes 'beard' (beard can mean 'confront' or 'challenge'**).
'blue'+'beard'='BLUEBEARD'
(Other definitions for bluebeard that I've seen before include "Legendary polygamist and wife-killer" , "Be durable (anag) - wife-murderer" , "murderous character" , "Villain with many wives" , "serial wife-killer" .)