No! Paragons aren't cast as undesirable! (7,3,5)
I believe the answer is:
persona non grata
'undesirable' is the definition.
(thesaurus)
'no paragons aren't cast' is the wordplay.
'cast' indicates an anagram.
'no'+'paragons'+'arent'='noparagonsarent'
'noparagonsarent' anagrammed gives 'PERSONA NON GRATA'.
'as' is the link.
(Other definitions for persona non grata that I've seen before include "One banned" , "Undesirable" .)