Habits of a wise man in America (6)
I believe the answer is:
usages
'habits' is the definition.
(I've seen this in another clue)
'a wise man in america' is the wordplay.
'a wise man' becomes 'sage' (sage is a kind of wise man).
'in' is an insertion indicator.
'america' becomes 'US' (United States).
'sage' put into 'us' is 'USAGES'.
'of' is the link.
(Other definitions for usages that I've seen before include "Customary treatments, practices" , "Habitual or customary practices" , "Linguistic norms" , "Habitual practices with words" , "speech patterns" .)