Sounding stuffy (5)
I believe the answer is:
nasal
'sounding stuffy' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nasal that I've seen before include "Of sound, as if it came through the nose" , "nozzle" , "Part of helmet" , "adenoids" , "front piece of helmet" .)