A noble’s quite revolutionary? It’s doubtful (12)
I believe the answer is:
questionable
'doubtful' is the definition.
(similar in meaning)
'a noble's quite revolutionary?' is the wordplay.
'revolutionary?' is an anagram indicator (I've seen 'revolutionary' mean this).
'a'+'nobles'+'quite'='anoblesquite'
'anoblesquite' with letters rearranged gives 'QUESTIONABLE'.
'it's' acts as a link.
(Other definitions for questionable that I've seen before include "Controversial" , "Suspect, unproven" , "Doubtful - possibly dishonest" , "Dubious" , "Open to doubt" .)