The most common and most likely answer to this crossword clue is the 7 letter word SACKBUT
I've seen this crossword clue in The Times
S
A
C
K
B
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T
More clues leading to the result SACKBUT
- Instrument in vessel about to go on fire
- Dismiss objection showing old-fashioned brass
- After pillage, save brass instrument
- Train of silk except that it could’ve been blown
- Initially seen as crazy, keep bringing up the old musical instrument
- Fire still in old instrument
- Instrument in boat capsized under fire
- Instrument taken from bag by Aunt Sally, briefly
- Under fire, however, players blew it
- Old instrument is still on fire
Buddy explains!

The straight part
We know that "old musical instrument" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old musical instrument = sackbut.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 SACKBUT mean?
SACKBUT noun- A brass instrument from the Renaissance and Baroque Eras, and an ancestor of the modern trombone. It was derived from the medieval slide trumpet.