Nothing that is right may be worse (9)
I believe the answer is:
naughtier
'be worse' is the definition.
(I've seen this before)
'nothing that is right' is the wordplay.
'nothing' becomes 'naught' ('naught' can be a synonym of 'nothing'**).
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'right' becomes 'r' (common abbreviation).
'naught'+'ie'+'r'='NAUGHTIER'
'may' acts as a link.
(Other definitions for naughtier that I've seen before include "Worse" , "More badly behaved" , "More mischievous" , "Less well behaved" , "more unruly" .)