The most common and most likely answer to this crossword clue is the 8 letter word BASILISK
I've seen this crossword clue in Financial Times
B
A
S
I
L
I
S
K
More clues leading to the result BASILISK
- Reptile is back, large one coming in to lie in the sun
- Sybil’s partner is known initially as one with a fearsome look
- Obsequious hotel owner is known primarily as a legendary slitherer
- Mr Fawlty is king? Here’s creature with lethal gaze!
- Bishop is interrupting a QC, fearful creature
- One lizard primarily lives in sun, like this tropical one?
- Herb’s grand old gun
- Primarily being a serpent in legend, its stare kills!
- Monster herb is Karen’s first
- Herb is known primarily as one with killer looks
Buddy explains!

The straight part
We know that "one with a fearsome look" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one with a fearsome look = basilisk.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 BASILISK mean?
BASILISK noun- A mythical (and heraldic) snake-like dragon type, reputed to be so venomous that its gaze was deadly.
- A type of dragon used in heraldry.
- A tree-dwelling type of lizard of the genus Basiliscus - the basilisk lizard
- A type of large brass cannon.
- Suggesting a basilisk (snake-like dragon): baleful, spellbinding.