The most common and most likely answer to this crossword clue is the 9 letter word MANNERISM
M
A
N
N
E
R
I
S
M
More clues leading to the result MANNERISM
- Flanked by a couple of maidens, king is after queen — a habit
- Peculiarity of foreign men in arms
- Peculiarity of chap raised alarm with maiden
- Chap raised alarm over minute quirk
- Peculiarity of bloke’s alarm over maiden
- Distinctive quality of absurd nonviolent environmentalism
- Idiosyncracy in merman's swimming
Buddy explains!

The straight part
We know that "a habit" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a habit = mannerism.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 MANNERISM mean?
MANNERISM noun- A noticeable personal habit, a verbal or other (often, but not necessarily unconscious) habitual behavior peculiar to an individual.
- Exaggerated or affected style in art, speech, or other behavior.
- In literature, an ostentatious and unnatural style of the second half of the sixteenth century. In the contemporary criticism, described as a negation of the classicist equilibrium, pre-Baroque, and deforming expressiveness.
- In fine art, a style that is inspired by previous models, aiming to reproduce subjects in an expressive language.