The most common and most likely answer to this crossword clue is the 5 letter word OCTET
I've seen this crossword clue in The Times
O
C
T
E
T
More clues leading to the result OCTET
- Surprisingly content to ignore every new music group
- Eight carat ring someone not from this world possesses
- What comes from sextet, couple turning up?
- Month ending with out-of-this world group performing
- Small group of commandos taking enemy territory at the front
- Month with alien group
- Performers etc involved in Old Testament
- Group in company set up before new year
- Group books about reversing and so on
- G8 company turning offensive
Buddy explains!

The straight part
We know that "group performing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case group performing = octet.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 OCTET mean?
OCTET noun- A group or set of eight of something.
- A group of eight musicians performing together.
- A composition for such a group of musicians.
- A byte of eight bits. Abbreviation: o
- A group of three bits, representing any of eight possible values.