Drunk swore — that's not so good (5)
I believe the answer is:
worse
'not so good' is the definition.
(I've seen this before)
'drunk swore' is the wordplay.
'drunk' is an anagram indicator.
'swore' with letters rearranged gives 'WORSE'.
'that's' acts as a link.
(Other definitions for worse that I've seen before include "Opposite of better" , "More severe; less well" , "Less good" , "More awful or unwell" , "Less satisfactory" .)