The most common and most likely answer to this crossword clue is the 4 letter word YOGH
Y
O
G
H
Buddy explains!

The straight part
We know that "an old character" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case an old character = yogh.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 YOGH mean?
YOGH noun- A letter of the Middle English alphabet (capital Ȝ, small ȝ), in form derived from the Old English shape of the letter g, and used to represent various palatal and velar sounds.