The most common and most likely answer to this crossword clue is the 13 letter word REARRANGEMENT
I've seen this crossword clue in The Times
R
E
A
R
R
A
N
G
E
M
E
N
T
More clues leading to the result REARRANGEMENT
- Behind mountains, intended, we hear, to form new organisation
- Raise stove intended, we hear, for a new layout
- An errant merge gone wrong could lead to this?
- Bring up oven before setter books alteration
- Shuffle back row organized to catch circling chaps
- After which Di and Teri become tidier?
- Shuffling back over mountains, chaps start to tire
- New organisation on Scottish isle get to recruit guys
Buddy explains!

The straight part
We know that "this?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case this? = rearrangement.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 REARRANGEMENT mean?
REARRANGEMENT noun- The process of rearranging.
- A rearrangement reaction.