The most common and most likely answer to this crossword clue is the 4 plus 4 letter word TONE POEM
I've seen this crossword clue in The Guardian
T
O
N
E
P
O
E
M
More clues leading to the result TONE POEM
- Unusual tempo to maintain one piece of music
- Writer upholding general quality shown by Mahler’s first musical composition
- To rejected author, free verse
- Twosome open Othello, some flipping piece!
- Piece of music with unusual tempo entertaining one
- Piece of music I put in frantic tempo
- ‘La Mer’, say, only in unusual tempo
- A petty officer joined up to cover work
- Retiring setter spread out books and a piece of music
Buddy explains!

The straight part
We know that "piece" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case piece = tone poem.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.