Language you can see with one eye (6)
I believe the answer is:
coptic
'language' is the definition.
(Coptic is an example)
'see with one eye' is the wordplay.
'see' becomes 'c' (the word for the letter, according to Chambers).
'with' means one lot of letters go next to another.
'one eye' becomes 'optic' ('optic' can be a synonym of 'eye').
'c'+'optic'='COPTIC'
'you can' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for coptic that I've seen before include "Egyptians in the past" , "Sweet; fungus" , "Egyptian church language" , "A language of Egypt" , "Ancient Christian church of Egypt" .)