Ring me for a speech sound (7)
I believe the answer is:
phoneme
'a speech sound' is the definition.
(phoneme is a kind of speech sound)
'ring me' is the wordplay.
'ring' becomes 'phone' (synonyms).
'phone'+'me'='PHONEME'
'for' acts as a link.
(Other definitions for phoneme that I've seen before include "minimal piece of speech" , "Small bit of speech" , "Unit of spoken sound" , "distinctive sound" .)