The most common and most likely answer to this crossword clue is the 0 letter word
More clues leading to the result
- Strut around Hamilton with pasty-eating top executive
- Birthday’s coming up: look to stop that old person's curse!
- this clue didn't remind anyone else of the epoch-shatteringly bad Bennifer movie...
- - CURTAIL [dock] replacing its last letter with... um, N for large? Think I'm missing something
- - AN NOD AM [an | agreement | earlier in the day] reversed
- - {br}ECHT - German playwrightlosing his BR for British
- - humorously misconstrued, if you only spend a single second in command, you've been a very short time at the top
- - double def
- BACK: double definition, the first facetious.
- IN, HALER. A pedant might object that it expands the bronchi, not the chest, but near enough.
Buddy explains!
The straight part
We know that "Upset once" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case upset once = .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.