The most common and most likely answer to this crossword clue is the 8 letter word URBANITY
I've seen this crossword clue in The Daily Telegraph
U
R
B
A
N
I
T
Y
More clues leading to the result URBANITY
Buddy explains!
The straight part
We know that "Courtesy/a quality of the townsman" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case courtesy/a quality of the townsman = urbanity.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 URBANITY mean?
URBANITY noun- Behaviour that is polished, refined, courteous.
- What is characteristically urban in an area; urbanness.