The most common and most likely answer to this crossword clue is the 6 letter word FORMER
I've seen this crossword clue in The Daily Telegraph
F
O
R
M
E
R
Buddy explains!

The straight part
We know that "Departed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case departed = former.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 FORMER mean?
FORMER adjective- Previous.
- First of aforementioned two items. Used with the, often without a noun.
- Someone who forms something; a maker; a creator or founder.
- An object used to form something, such as a template, gauge, or cutting die.
- (used in combinations) Someone in, or of, a certain form (class).