It's Latin, you idiot girl! (4)
I believe the answer is:
lass
'girl' is the definition.
(lass can informally mean a girl)
'it's latin you idiot' is the wordplay.
I cannot really understand how this works, but
'latin' could be 'l' and 'l' is present in the answer.
'idiot' could be 'ass' (I've seen this in other clues) and 'ass' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for lass that I've seen before include "Damsel" , "Scottish girl" , "Sweet resident of Richmond Hill?" , "Young woman, girl" , "Girl (of Richmond Hill?)" .)