The most common and most likely answer to this crossword clue is the 8 letter word ABSENTEE
I've seen this crossword clue in Financial Times
A
B
S
E
N
T
E
E
More clues leading to the result ABSENTEE
- One’s missing, having been east on tour
- Missing person dispatched during a competition
- A bishop ‘delivered’ by drug– he’s at another place
- Skiver ecstatic, a worker claims
- One missing president, tense, upset inwardly
- Peg’s after a playwright? Not the one who’s never arrived
- American, busy worker posted in for one away
- Tea’s been set out – one is missing
- Malingerer maybe transported when a hard worker’s around
- Sailor posted to Eastern Europe is a missing person
Buddy explains!

The straight part
We know that "one is missing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one is missing = absentee.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 ABSENTEE mean?
ABSENTEE noun- A person who is absent from his or her employment, school, post, duty, etc.
- A landholder who lives in another district or country than the one in which his estate is situated.
- One that is nonexistent or lacking.
- A voter that is not present at the time of voting; absentee voter.
- Pertaining to one that is absent.