I’ll wait for you to call Linguistic Unit (7)
I believe the answer is:
phoneme
'linguistic unit' is the definition.
(phoneme is a kind of linguistic unit)
'i'll wait for you to call' is the wordplay.
I cannot really understand how this works, but
'you' could be 'one' (I've seen this before) and 'one' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for phoneme that I've seen before include "Unit of spoken sound" , "Small bit of speech" , "distinctive sound" , "minimal piece of speech" .)