The most common and most likely answer to this crossword clue is the 8 letter word ALL-STAR
I've seen this crossword clue in The Guardian
A
L
L
-
S
T
A
R
More clues leading to the result ALL-STAR
Buddy explains!
The straight part
We know that "belonging to an outstanding group" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case belonging to an outstanding group = all-star.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 ALL-STAR mean?
ALL-STAR noun- A member of a team of star players.
- Of which all members or participants are celebrities.