The most common and most likely answer to this crossword clue is the 8 letter word DAUNTING
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More clues leading to the result DAUNTING
Buddy explains!

The straight part
We know that "rather scary" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rather scary = daunting.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 DAUNTING mean?
DAUNTING verb- To discourage, intimidate.
- To overwhelm.
- Present participle of daunt.
- Discouraging; inspiring fear.
- Intimidatingly impressive; awe-inspiring, overwhelming.
- Appearing to be difficult; challenging.