Putting in case for sport (6)
I believe the answer is:
boxing
This clue is a double definition.
'putting in case' is the first definition.
'sport' is the second definition.
(boxing is a kind of sport)
'for' acts as a link.
(Other definitions for boxing that I've seen before include "handling rights, possibly?" , "Pugilist's sport" , "Sport of Bruno, Tyson and Lewis" , "The noble art?" , "Fighting with the fists" .)