Owing to student contest (4)
I believe the answer is:
duel
'contest' is the definition.
(fight between two people)
'owing to student' is the wordplay.
'owing' becomes 'due' (similar in meaning).
'to' is a charade indicator (letters next to each other).
'student' becomes 'l' (as in L-plates for learner drivers).
'due'+'l'='DUEL'
(Other definitions for duel that I've seen before include "Single combat" , "Gentlemen's disagreement" , "Affaire d'honneur" , "Contest between two with deadly weapons" , "honourable affair" .)