The most common and most likely answer to this crossword clue is the 8 letter word ALPHABET
I've seen this crossword clue in Financial Times
A
L
P
H
A
B
E
T
More clues leading to the result ALPHABET
- All the letters of Plath Bea devoured
- Peak support involving husband and lots of characters
- Characters offering help below mountain height
- Does it store all the letters one writes?
- Some characters moving a table outside pub
- Group of characters in The Rover heading off on a venture?
- Elements of type found within spermatozoa
- Letters from mountain hospital: help!
- Every letter is written in it
- Every character raising a drink to inspire pub during party
Buddy explains!

The straight part
We know that "Every character" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case every character = alphabet.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 ALPHABET mean?
ALPHABET noun- The set of letters used when writing in a language.
- A writing system in which letters represent phonemes. (Contrast e.g. logography, a writing system in which each character represents a word, and syllabary, in which each character represents a syllable.)
- A typically finite set of distinguishable symbols.
- An individual letter of an alphabet; an alphabetic character.
- The simplest rudiments; elements.
- To designate by the letters of the alphabet; to arrange alphabetically.