The most common and most likely answer to this crossword clue is the 6 letter word BELTER
I've seen this crossword clue in Independent
B
E
L
T
E
R
More clues leading to the result BELTER
Buddy explains!
The straight part
We know that "Something outstandingly good" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case something outstandingly good = belter.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 BELTER mean?
BELTER noun- Anything that is particularly good of its class.
- A very good-looking person.
- One who sings forcefully.
- A song suitable for forceful singing.
- A person who mines asteroids for minerals or lives in the vicinity of an asteroid belt.