Practice at home ground (7)
I believe the answer is:
habitat
'home ground' is the definition.
(I've seen this before)
'practice at' is the wordplay.
'practice' becomes 'habit' (habit is a kind of practice).
'habit'+'at'='HABITAT'
(Other definitions for habitat that I've seen before include "Living area" , "Environment in which groups normally live" , "Natural home of a plant or animal" , "One's normal environment" , "Natural home of an organism" .)