The most common and most likely answer to this crossword clue is the 10 letter word BOTTICELLI
I've seen this crossword clue in The Times
B
O
T
T
I
C
E
L
L
I
More clues leading to the result BOTTICELLI
- He painted bishop with bad back gulping too much cold water
- Horrible smell I detected in dry part of prison - one painter required!
- Artist showing a lot of daring around rocks, taking end of chisel to one
- Artist, extravagant in book pair presented about small group
- Painter‘s bill to cite rework
- Artist initially bears excessive chill, turning poorly
- Artist born with excessive diamonds rejecting 75% of will
- Artist getting limited credit in waterside accommodation on large island
- Beginning to be histrionic, one with small room, one who painted?
- Italian artist‘s belt — coil it for sculpting
Buddy explains!

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