Nasal explosion (6)
I believe the answer is:
sneeze
'nasal explosion' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sneeze that I've seen before include "Prelude to Bless you!" , "Explosion of air through nose and mouth" , "symptom of flu" , "Symptom of cold" , "To which gesundheit is often a response" .)