Malign grandee: "out with it!" (9)
I believe the answer is:
denigrate
'malign' is the definition.
(I know that malign is a more specific form of denigrate)
'grandee out with it' is the wordplay.
'out with' is an anagram indicator (out can mean wrong or inaccurate).
'grandee' anagrammed with 'it' makes 'DENIGRATE'.
(Other definitions for denigrate that I've seen before include "Slight" , "Defame" , "put down" , "Blacken" , "Run down" .)