Uncertain about noisy Yankee (6)
I believe the answer is:
cloudy
'uncertain' is the definition.
(I've seen this in another clue)
'about noisy yankee' is the wordplay.
'about' becomes 'c' (abbreviation for circa).
'noisy' becomes 'loud' (associated in meaning).
'yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'c'+'loud'+'y'='CLOUDY'
(Other definitions for cloudy that I've seen before include "(Of a liquid) not clear" , "Murky or nebulous" , "It's unclear" , "Obscure" , "Blurred" .)