The most common and most likely answer to this crossword clue is the 8 letter word FIGURANT
F
I
G
U
R
A
N
T
More clues leading to the result FIGURANT
Buddy explains!

The straight part
We know that "Ballet-dancer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ballet-dancer = figurant.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 FIGURANT mean?
FIGURANT noun- An actor or dancer in the background lacking an aural presence.