Make call to the writer in linguistics unit (7)
I believe the answer is:
phoneme
'unit' is the definition.
(I have seen 'sound unit' mean 'phoneme' so perhaps 'unit' could also mean 'phoneme')
'make call to the writer in linguistics' is the wordplay.
I cannot quite see how this works, but
'call' could be 'phone' (phone can mean to call by telephone) and 'phone' is present in the answer.
'writer' could be 'me' (the person who wrote the clues) and 'me' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for phoneme that I've seen before include "distinctive sound" , "Unit of spoken sound" , "minimal piece of speech" , "Small bit of speech" .)