The most common and most likely answer to this crossword clue is the 4 plus 3 plus 6 letter word AIRS AND GRACES
I've seen this crossword clue in The Times
A
I
R
S
A
N
D
G
R
A
C
E
S
More clues leading to the result AIRS AND GRACES
Buddy explains!
The straight part
We know that "superior manners" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case superior manners = airs and graces.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.