In the south of Italy, it’s perfectly proper (3)
I believe the answer is:
fit
'perfectly proper' is the definition.
'fit' can be an answer for 'proper' (thesaurus). I'm not certain of the 'perfectly' bit.
'in the south of italy it's' is the wordplay.
'in the south' suggests the final letters (I've seen 'in the south of' mean this (in a down clue, the bottom letter)).
'italy' becomes 'i'.
'it' becomes 't' (abbreviation. e.g. in 'tis**).
The final letter of 'of' is 'f'.
'f'+'i'+'t'='FIT'
Can you help me to learn more?
(Other definitions for fit that I've seen before include "In good shape; sudden attack" , "Be the right size or shape" , "In trim" , "Match" , "Appropriate -- not 21" .)