The most common and most likely answer to this crossword clue is the 8 letter word DESOLATE
I've seen this crossword clue in Financial Times
D
E
S
O
L
A
T
E
More clues leading to the result DESOLATE
- Unhappy miss, having been stood up, laid into boyfriend?
- Bare bottoms in England are very overdue
- Fail to keep up in time? Wretched!
- Greatly upset dinner partner – forget to go back inside
- Fail to get back in time, becoming sad
- Lonely miss stood up during tryst
- Fail to return during assignation, upset
- Wretched lower grades showing such tardiness
- Forlorn sweetheart almost alone in rendezvous
- … abandoned and depressed
Buddy explains!

The straight part
We know that "upset" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case upset = desolate.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 DESOLATE mean?
DESOLATE verb- To deprive of inhabitants.
- To devastate or lay waste somewhere.
- To abandon or forsake something.
- To make someone sad, forlorn and hopeless.
- Deserted and devoid of inhabitants.
- Barren and lifeless.
- Made unfit for habitation or use because of neglect, destruction etc.
- Dismal or dreary.
- Sad, forlorn and hopeless.