Unacceptable in the south (3)
I believe the answer is:
out
'unacceptable' is the definition.
(out can mean incorrect or inappropriate)
'in the south' is the wordplay.
'in' indicates the answer is hidden within the clue.
'OUT' can be found hidden inside 'south'.
(Other definitions for out that I've seen before include "SECOND PART OF 16" , "In error" , "Disnmissed (cricket)" , "No longer in prison" , "Possibly caught" .)