Plain rude -- and no different (9)
I believe the answer is:
unadorned
'plain' is the definition.
('unadorned' can be similar in meaning to 'plain')
'rude and no different' is the wordplay.
'different' indicates an anagram.
'rude'+'and'+'no'='rudeandno'
'rudeandno' anagrammed gives 'UNADORNED'.
(Other definitions for unadorned that I've seen before include "Not decorated, plain and simple" , "Plain, undecorated" , "Without embellishment" , "Simple and plain as around den" .)