Pronunciation symbol (5)
I believe the answer is:
schwa
'pronunciation symbol' 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 "Uh' sound" , "Unstressed vowel (phonetics)" , "Indistinct sound" , "Stress-free sound" , "sound unstressed" .)