Good loser is fun (5)
I believe the answer is:
sport
I believe this clue is a double definition.
'good loser' is the first definition.
(I've seen this in another clue)
'fun' is the second definition.
(I know that fun can be written as sport)
'is' is the link.
(Other definitions for sport that I've seen before include "eg Tennis" , "Recreation, play" , "Put on" , "Eg, rugby" , "Eg, football; fun" .)