The most common and most likely answer to this crossword clue is the 6 letter word CREEPY
I've seen this crossword clue in The Times
C
R
E
E
P
Y
More clues leading to the result CREEPY
- Pony disembowelled by Indian? That’s disturbing
- Frightening member of tribe? Pray, if losing heart
- Sinister rising member of upper house cutting Young Conservatives
- Bug eerie East Sussex town picked up
- Sinister howl goes round tower after beheading
- Weep about European record being unsettling
- Sinister look is arising in case of cowboy
- Constituents of randy peer caught rolling like dirty old men
- Keen to bury leak, head-er deleted as sinister
- Scary Indian emptying larder
Buddy explains!

The straight part
We know that "Frightening" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case frightening = creepy.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 CREEPY mean?
CREEPY adjective- Moving by creeping along.
- Producing an uneasy fearful sensation, as of things crawling over one's skin.
- Feeling an uneasy fearful sensation; creeped out.
- Strangely repulsive.