The most common and most likely answer to this crossword clue is the 6 letter word FACIES
I've seen this crossword clue in The Guardian
F
A
C
I
E
S
Buddy explains!

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 FACIES mean?
FACIES noun- Appearance.
- Facial features, like an expression or complexion, typical for patients having certain diseases or conditions.
- A body of rock with specified characteristics reflecting the way it was formed.