Neutral vowel (5)

I believe the answer is:
schwa
'neutral vowel' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for schwa that I've seen before include "Indistinct sound" , "Unstressed vowel (phonetics)" , "Stress-free sound" , "Uh' sound" , "sound unstressed" .)