The most common and most likely answer to this crossword clue is the 6 letter word FRESCO
I've seen this crossword clue in The Times
F
R
E
S
C
O
More clues leading to the result FRESCO
- Wall covering scattered forces
- Painting Al’s left in the open air
- Officer commanding lowly worker to bring back work of art
- Slave turns up with company artwork
- Work of art characterised by originality largely, oddly cool
- Forces assembled for The Last Supper, say
- Largely original company painting
- Opening for film score in motion picture
- Bondsman brought back firm’s painting
- Firm is after almost new painting
Buddy explains!

The straight part
We know that "work of art" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case work of art = fresco.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 FRESCO mean?
FRESCO noun- A cool, refreshing state of the air; coolness, duskiness, shade.
- An artwork made by applying water-based pigment to wet or fresh lime mortar or plaster.
- The technique used to make such an artwork.
- To paint using fresco.