The most common and most likely answer to this crossword clue is the 8 letter word ALARMIST
I've seen this crossword clue in Independent
A
L
A
R
M
I
S
T
More clues leading to the result ALARMIST
- Causing fear, in the manner of end of horror film
- A catalogue contains weapon, scandalmonger revealed
- Limb caught in a register, I’d be worried by that
- Wake-up call first for Cassandra?
- One magnifies danger in local armistice
- One panics, shoving weapon into a tip
- Top celebrities tooled up? One worries unduly
- Scaremonger with anxious air almost devoid of love
- Panicking member overwhelmed by Article 50 – “it’s triggered!”
- Member in a register, scaremonger
Buddy explains!

The straight part
We know that "Cassandra?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cassandra? = alarmist.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 ALARMIST mean?
ALARMIST noun- One who causes others to become alarmed without cause.
- Of or relating to causing others to become alarmed without cause.