The most common and most likely answer to this crossword clue is the 11 letter word MANHANDLING
I've seen this crossword clue in The Guardian
M
A
N
H
A
N
D
L
I
N
G
Buddy explains!

The straight part
We know that "rough treatment" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rough treatment = manhandling.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 MANHANDLING mean?
MANHANDLING verb- To move something heavy by force of men, without aid of levers, pulleys, machine, or tackles.
- To assault or beat up a person.
- To mishandle; to handle roughly; to mangle.
- To control (a machine, vehicle, situation, etc.) by means of physical strength.