The most common and most likely answer to this crossword clue is the 8 letter word PAGANINI
I've seen this crossword clue in The Guardian
P
A
G
A
N
I
N
I
More clues leading to the result PAGANINI
- What’s at the heart of propaganda, Leninist, he composed
- Treat angina in religious Bow man
- Bread stuffed with skin of guava for star 12
- A great fiddler, one not believing in integrity, initially
- Italian barman and female, seen through one window, both having retired …
- Trendy pair are opening up to musician
- Heathen in Italy often on the fiddle
- Old bower, non-Christian in one
- Pain and gain makes a great violinist
- Someone lacking faith in one violinist
Buddy explains!

The straight part
We know that "star 12" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case star 12 = paganini.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.