The most common and most likely answer to this crossword clue is the 8 plus 10 letter word INTERIOR DECORATION
I've seen this crossword clue in The Times
I
N
T
E
R
I
O
R
D
E
C
O
R
A
T
I
O
N
Buddy explains!
The straight part
We know that "Job for painter" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case job for painter = interior decoration.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.