The Italian assistant noted last letter is from South American location (5)
I believe the answer is:
lapaz
'letter is from south american location' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'the italian assistant noted last' is the wordplay.
'the italian' becomes 'la' ('the' in Italian).
'assistant' becomes 'PA' (personal assistant).
'noted last' becomes 'z' (Last letter alphabet. I am not sure about the 'noted' bit.).
'la'+'pa'+'z'='LAPAZ'
Can you help me to learn more?
(Another definition for lapaz that I've seen is " City at high altitude".)