Practice in America over long time (5)
I believe the answer is:
usage
'practice' is the definition.
(I know that usage is a type of practice)
'america over long time' is the wordplay.
'america' becomes 'US' (United States).
'over' is a charade indicator (letters next to each other).
'long time' becomes 'age' (an age is a period of time).
'us'+'age'='USAGE'
'in' acts as a link.
(Other definitions for usage that I've seen before include "Style of language" , "Interest of old" , "Acceptable language" , "Habit" , "Established custom" .)