The most common and most likely answer to this crossword clue is the 8 letter word DIVORCED
I've seen this crossword clue in Independent
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More clues leading to the result DIVORCED
Buddy explains!

The straight part
We know that "separated" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case separated = divorced.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 DIVORCED mean?
DIVORCED verb- To legally dissolve a marriage between two people.
- To end one's own marriage to (a person) in this way.
- To obtain a legal divorce.
- To separate something that was connected.
- Cut off, or separated.
- (of a marriage) Legally dissolved.
- (of persons formerly married) Having had one's marriage legally dissolved.