The most common and most likely answer to this crossword clue is the 10 letter word NEAPOLITAN
I've seen this crossword clue in The Times
N
E
A
P
O
L
I
T
A
N
More clues leading to the result NEAPOLITAN
- Not a Nepali misbehaving — someone else entirely
- Italian's explanation resolved missing vote
- Neat, polite and not totally Italian
- To an alpine resort to find an Italian
- Ice-cream option, on plate, in a shambles
- See about leaving fresh pie ‘alla tonno’ from Campania?
- Old writer upset about a form of Latin from place in Italy
- Italian staggered into a plane
- Elton with a piano cut short broadcast from somewhere in Italy
- When ill, eat no plain chocolate
Buddy explains!
The straight part
We know that "someone else entirely" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case someone else entirely = neapolitan.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.