The most common and most likely answer to this crossword clue is the 8 plus 7 letter word KANGAROO JUSTICE
I've seen this crossword clue in The Times
K
A
N
G
A
R
O
O
J
U
S
T
I
C
E
Buddy explains!
The straight part
We know that "rough sentences" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rough sentences = kangaroo justice.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.