The most common and most likely answer to this crossword clue is the 6 letter word UNCIAL
I've seen this crossword clue in Financial Times
U
N
C
I
A
L
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 UNCIAL mean?
UNCIAL adjective- Of or relating to an ounce, or an inch, especially to letters printed an inch high.
- A style of writing using uncial letters.
- A letter in this style.
- A manuscript in this style.
- Of or relating to a majuscule style of writing with unjoined, rounded letters, originally used in the 4th–9th centuries.