The most common and most likely answer to this crossword clue is the 7 letter word LOUTISH
I've seen this crossword clue in Independent
L
O
U
T
I
S
H
More clues leading to the result LOUTISH
- Unmannerly leaders of illegal sect in Irish county
- Time to supplant Democrat, quite noisy and uncouth
- Ill-mannered unionist among group is close to Taoiseach
- In part of Ireland, is uncouth and aggressive
- Ill-mannered unionist in group is facing hospital
- . It's gross to have misused his authority — leader ousted to start with
Buddy explains!

The straight part
We know that "Ill-mannered" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ill-mannered = loutish.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 LOUTISH mean?
LOUTISH adjective- Resembling a lout.