"Gesundheit!" elicitor
'gesundheit elicitor' 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!" , "reason for blessing" , "Involuntary expiration of air" , "Expel air from nose" , "Sign of a cold or flu" .)