The most common and most likely answer to this crossword clue is the 6 letter word PLAINT
I've seen this crossword clue in The Daily Telegraph
P
L
A
I
N
T
More clues leading to the result PLAINT
- Moan one's stuck in factory
- Cry from one trapped by machinery
- Sad song from Italy young person’s penned
- Beef dish from Paris fed One Direction
- Factory receiving one statement of grievance
- Obvious time for mournful song
- Dirge from one entering works
- Mournful song from Led Zeppelin singer penning single
- Works to get across independent statement of grievance
- Cry from one trapped in factory
Buddy explains!

The straight part
We know that "mournful song" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mournful song = plaint.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 PLAINT mean?
PLAINT noun- A lament or woeful cry.
- A complaint.
- A sad song.
- An accusation.