The most common and most likely answer to this crossword clue is the 6 letter word RUEFUL
I've seen this crossword clue in Financial Times
R
U
E
F
U
L
More clues leading to the result RUEFUL
- Bitter herb dock packed makes you apologetic
- Melancholy way of the French footloose rich
- Four regularly break new rule, repenting
- Almost bursting on Parisian street? In a sorry state!
- Sheepish four regularly breaking new rule
- Nice street almost packed – sorry!
- Melancholy skipper with no more appetite, we’re told
- Endless enjoyment breaking rule naughtily making one sorry
- Sorry for sport fan with English leading
- Regretting using Parisian street that’s almost completely jammed
Buddy explains!

The straight part
We know that "Melancholy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case melancholy = rueful.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 RUEFUL mean?
RUEFUL adjective- Causing, feeling, or expressing regret or sorrow, especially in a wry or humorous way.
- Inspiring pity or compassion.
- Bad; woeful; deplorable.