The most common and most likely answer to this crossword clue is the 8 letter word COASTERS
I've seen this crossword clue in Financial Times
C
O
A
S
T
E
R
S
More clues leading to the result COASTERS
Buddy explains!
The straight part
We know that "group singing “Yakety-Yak”" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case group singing “yakety-yak” = coasters.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 COASTERS mean?
COASTERS noun- Agent noun of coast: one who coasts.
- Something that coasts, such as a sled or toboggan.
- A merchant vessel that stays in coastal waters.
- A sailor who travels only in coastal waters.
- A person who originates from or inhabits a coastal area.
- A small piece of material used to protect the surface of a table, upon which one places cups or mugs.
- A small tray on wheels, used to pass something around a table.
- A worthless compact disc or DVD, such as one that was burned incorrectly.
- A rollercoaster.
- (Lake Superior) A coaster trout (brook trout, Salvelinus fontinalis)
- A prostitute, especially a white woman, plying her trade in Chinese port towns.