Often the sound of the school was reduced (5)
I believe the answer is:
schwa
'often the sound of' is the definition.
I can't tell whether this definition defines the answer.
'school was reduced' is the wordplay.
'school' becomes 'sch' (common abbreviation).
'reduced' means to remove the last letter.
'was' with its final letter taken away is 'wa'.
'sch'+'wa'='SCHWA'
'the' is the link.
Can you help me to learn more?
(Other definitions for schwa that I've seen before include "Uh' sound" , "Stress-free sound" , "Indistinct sound" , "sound unstressed" , "Unstressed vowel (phonetics)" .)