A habit socially acceptable and wise (5)
I believe the answer is:
usage
'a habit' is the definition.
(I've seen this in another clue)
'socially acceptable and wise' is the wordplay.
'socially acceptable' becomes 'U' (as in U and non-U language).
'and' means one lot of letters go next to another.
'wise' becomes 'sage' (similar in meaning).
'u'+'sage'='USAGE'
(Other definitions for usage that I've seen before include "Way of treating" , "Tradition - rate of consumption" , "Convention" , "etiquette" , "Habitual custom" .)