Give me a call with a smallest distinct unit of sound (7)
I believe the answer is:
phoneme
'sound' is the definition.
(speech sound)
'give me a call with a smallest distinct unit' is the wordplay.
I cannot quite see how this works, but
'me' could be 'one' (I've seen this in other clues) and 'one' is present in the answer.
'unit' could be 'hm' (hm is a kind of unit) and 'hm' is present in the remaining letters.
This explanation may well be incorrect...
'of' is the link.
Can you help me to learn more?
(Other definitions for phoneme that I've seen before include "minimal piece of speech" , "Small bit of speech" , "Unit of spoken sound" , "distinctive sound" .)