The most common and most likely answer to this crossword clue is the 4 plus 4 letter word SWAN SONG
I've seen this crossword clue in The Guardian
S
W
A
N
S
O
N
G
More clues leading to the result SWAN SONG
- Last appearance by Gloria – and her first!
- Final appearance of pale lad in middle of Ramsgate
- Issue stops champs returning for final appearance
- It could be a penchant for the final performance
- New boy dips into illicit money, a career-ending moment
- Pen a final ditty?
- Final appearance of Desmond, N in Sunset Boulevard
- Small pale child good giving ultimate performance
- 10’s offspring boarding vacant swing for a final effort
- Cob on lad, prior to good final performance!
Buddy explains!

The straight part
We know that "career-ending moment" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case career-ending moment = swan song.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.