The most common and most likely answer to this crossword clue is the 6 letter word SPOOKY
I've seen this crossword clue in The Guardian
S
P
O
O
K
Y
More clues leading to the result SPOOKY
Buddy explains!

The straight part
We know that "weird" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case weird = spooky.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 SPOOKY mean?
SPOOKY adjective- Eerie, or suggestive of ghosts or the supernatural.
- Spooked; afraid; frightened.
- Unpredictably excitable; skittish (used especially of horses).