The most common and most likely answer to this crossword clue is the 8 letter word RIGADOON
I've seen this crossword clue in The Guardian
R
I
G
A
D
O
O
N
Buddy explains!

The straight part
We know that "12/12" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case 12/12 = rigadoon.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 RIGADOON mean?
RIGADOON noun- A quickstep dance for two people.
- The music for this dance.
- Formerly in the French army, the beat of a drum while culprits were being marched to punishment.