The most common and most likely answer to this crossword clue is the 9 letter word BRUSHWORK
I've seen this crossword clue in The Daily Telegraph
B
R
U
S
H
W
O
R
K
Buddy explains!
The straight part
We know that "the technique of an artist" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the technique of an artist = brushwork.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.
What does BRUSHWORK mean?
BRUSHWORK noun- The technique or practice of applying and manipulating paint (usually oil or gouache) in a painting.