The most common and most likely answer to this crossword clue is the 9 letter word MAHLSTICK
I've seen this crossword clue in The Guardian
M
A
H
L
S
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K
Buddy explains!
The straight part
We know that "It helps an artist" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it helps an artist = mahlstick.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 MAHLSTICK mean?
MAHLSTICK noun- A short stick with a pad on one end, used by a painter to steady their hand, and to prevent it from accidentally touching the painting.