The most common and most likely answer to this crossword clue is the 11 letter word MIDDLEMARCH
I've seen this crossword clue in Independent
M
I
D
D
L
E
M
A
R
C
H
More clues leading to the result MIDDLEMARCH
Buddy explains!
The straight part
We know that "24/24" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case 24/24 = middlemarch.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.