The most common and most likely answer to this crossword clue is the 8 letter word TROMBONE
I've seen this crossword clue in Financial Times
T
R
O
M
B
O
N
E
More clues leading to the result TROMBONE
- Traveller cutting steak produces an instrument
- Doctor entering course with little energy finds instrument
- Time that’s good in French in capital
- Some brass rubbings orginally pinched by grave individual
- One’s blown millions pursuing stardom, regularly revealing part of body
- Good French needed in Metro in order to play this
- Character touring storage facility with book, source of notes
- Instrument produced by gypsy chap cutting steak
- Mike with bogey at first in golf course facing east? Blow it!
- Instrument‘s bent with room to play
Buddy explains!

The straight part
We know that "Some brass" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case some brass = trombone.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 TROMBONE mean?
TROMBONE noun- A musical instrument in the brass family, having a cylindrical bore, and usually a sliding tube (but sometimes piston valves, and rarely both). Most often refers to the tenor trombone, which is the most common type of trombone and has a fundamental tone of B♭ˌ (contra B♭).
- The common European bittern.
- To transmit a signal or data back to a central switching point before sending it out to its destination.
- To extend and retract (the zoom lens); to use it too enthusiastically.