The most common and most likely answer to this crossword clue is the 9 letter word TRIPTYCHS
I've seen this crossword clue in The Guardian
T
R
I
P
T
Y
C
H
S
More clues leading to the result TRIPTYCHS
Buddy explains!

The straight part
We know that "series of art works" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case series of art works = triptychs.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 TRIPTYCHS mean?
TRIPTYCHS noun- A picture or series of pictures painted on three tablets connected by hinges.
- A set of three se-tenant postage stamps that form a composite picture.