Wrong choice crucial in this sport (3,6)
I believe the answer is:
ice hockey
'this sport' is the definition.
(ice hockey is a kind of sport)
'wrong choice crucial' is the wordplay.
'wrong' is an anagram indicator.
'crucial' becomes 'key' (I've seen this before).
'choice' is an anagram of 'icehoc'.
'icehoc'+'key'='ICE-HOCKEY'
'in' acts as a link.
(Other definitions for ice hockey that I've seen before include "Violent sport, big in North America" , "Team game played with long sticks" , "Game played by skaters with a puck" , "Sport with puck" .)