The most common and most likely answer to this crossword clue is the 12 letter word NATURALISTIC
I've seen this crossword clue in The Times
N
A
T
U
R
A
L
I
S
T
I
C
More clues leading to the result NATURALISTIC
Buddy explains!

The straight part
We know that "like Pre-Raphaelite painting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case like pre-raphaelite painting = naturalistic.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 NATURALISTIC mean?
NATURALISTIC adjective- Having the appearance of nature or realism; lifelike or realistic.
- Of or relating to philosophical or methodological naturalism.