The most common and most likely answer to this crossword clue is the 10 plus 4 letter word THREE-LINE WHIP
I've seen this crossword clue in Independent
T
H
R
E
E
-
L
I
N
E
W
H
I
P
More clues leading to the result THREE-LINE WHIP
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? = three-line whip.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.