Initially type of noise emitting air (4)
I believe the answer is:
tone
'air' is the definition.
(thesaurus)
'initially type of noise emitting' is the wordplay.
'initially' indicates taking the first letters.
The initial letters of 'type of noise emitting' is 'TONE'.
(Other definitions for tone that I've seen before include "Bodily firmness" , "A pitch of note" , "Quality or character of sound" , "Theobald Wolf . . . ." , "Musical sound of note" .)