It’s got to fix a note up (7)
I believe the answer is:
italian
'it's' is the definition.
('it' can be short for Italian)
'got to fix a note up' is the wordplay.
'got to' becomes 'it' (I can't explain this - if you can you should believe this answer much more).
'fix' becomes 'nail' (I've seen this before).
'a note' becomes 'a' (musical note).
'up' is a reversal indicator (in down clue: letters go upwards).
'nail'+'a'='naila'
'naila' backwards is 'alian'.
'it'+'alian'='ITALIAN'
Can you help me to learn more?
(Other definitions for italian that I've seen before include "Eg, Native of Turin" , "Ain't Ali out of Rome, perhaps?" , "European tongue" , "From Naples or Turin, perhaps?" , "Language of modern Rome" .)