Enclosure for sport (7)
I believe the answer is:
fencing
I believe this clue is a double definition.
'enclosure' is the first definition.
(I've seen this before)
'for sport' is the second definition.
(I've seen this before)
(Other definitions for fencing that I've seen before include "Olympic sport since 1896" , "Sport with swords" , "enclosure" , "Barrier; sport" .)