The most common and most likely answer to this crossword clue is the 6 plus 5 letter word MIDDLE EARTH
I've seen this crossword clue in The Guardian
M
I
D
D
L
E
E
A
R
T
H
More clues leading to the result MIDDLE EARTH
Buddy explains!
The straight part
We know that "Tolkien’s art?/Tolkien’s art?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tolkien’s art?/tolkien’s art? = middle earth.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.