The most common and most likely answer to this crossword clue is the 12 letter word MISALIGNMENT
I've seen this crossword clue in The Sunday Telegraph
M
I
S
A
L
I
G
N
M
E
N
T
Buddy explains!
The straight part
We know that "bad omen in stars?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bad omen in stars? = misalignment.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 MISALIGNMENT mean?
MISALIGNMENT noun- The state, or an instance, of being misaligned