Had on about South being not as good (5)
I believe the answer is:
worse
'not as good' is the definition.
(I've seen this in another clue)
'had on about south' is the wordplay.
'had on' becomes 'wore' ('wear' can be a synonym of 'have on').
'about' is an insertion indicator.
'south' becomes 's' (abbreviation).
'wore' placed around 's' is 'WORSE'.
'being' acts as a link.
(Other definitions for worse that I've seen before include "More severe; less well" , "More serious" , "Of poorer quality" , "More awful or unwell" , "Less good" .)