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