The most common and most likely answer to this crossword clue is the 7 letter word SADNESS
I've seen this crossword clue in The Daily Telegraph
S
A
D
N
E
S
S
More clues leading to the result SADNESS
- . The Blues retrospectively send in crack team
- Misery afflicted Danes boarding ship
- Injured Danes coming aboard in gloom
- Retired Irishman’s first to start singing the blues
- The Blues Brothers send a solo piece back
- Special forces capturing rebel ends in grief
- Small notice over head brings sorrow
- Dejection ends as first sign of smile breaks out
- Regret seeing ship’s stern while capsizing
- Low quality?
Buddy explains!

The straight part
We know that "Dejection" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dejection = sadness.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 SADNESS mean?
SADNESS noun- The state or emotion of being sad.
- An event in one's life that causes sadness.