The most common and most likely answer to this crossword clue is the 7 letter word SEQUINS
I've seen this crossword clue in Independent
S
E
Q
U
I
N
S
More clues leading to the result SEQUINS
Buddy explains!
The straight part
We know that "thousands on 6 24 21" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case thousands on 6 24 21 = sequins.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 SEQUINS mean?
SEQUINS noun- Any of various small gold coins minted in Italy and Turkey.
- A sparkling spangle used for the decoration of ornate clothing.