The most common and most likely answer to this crossword clue is the 7 letter word REMORSE
R
E
M
O
R
S
E
More clues leading to the result REMORSE
- Regret referring to signalling code
- Regret group of soldiers succeeded, blocking another group
- Some err, generating this?
- Pity he's left here gloomy, having lost second round
- Deep regret about bit of food, almost
- Shame about son taken in to a greater extent
- Shame troops seizing southern capital in rebellion
- Deep regret as vibrations not leading to ecstasy
- Shame about son going inside again
- Contrition shown by rock band found with heroin? Not at first
Buddy explains!

The straight part
We know that "Deep regret" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case deep regret = remorse.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 REMORSE mean?
REMORSE noun- A feeling of regret or sadness for doing wrong or sinning.
- Sorrow; pity; compassion.