Bit of southern rubbish (5)
I believe the answer is:
scrap
'bit' is the definition.
(I know that bit can be written as scrap)
'southern rubbish' is the wordplay.
'southern' becomes 's' (abbreviation).
'rubbish' becomes 'crap'.
's'+'crap'='SCRAP'
'of' acts as a link.
(Other definitions for scrap that I've seen before include "bundle" , "row" , "rubbish" , "Fragment or morsel" , "Carps (anag.)" .)