The most common and most likely answer to this crossword clue is the 7 letter word PORTENT
I've seen this crossword clue in The Daily Telegraph
P
O
R
T
E
N
T
More clues leading to the result PORTENT
- Sign in entrance letting number in
- Potter somehow minding Ron’s final warning
- Sign left on hospital department
- Catch thrown back in harbour, a bad sign
- Sign left at front of hospital department
- 10 left baffling sign
- Sign left carrying 10
- Take in strong warning
- Hospital department supports alcohol warning
- Warning — river beginning to rise. shelter!
Buddy explains!
The straight part
We know that "Warning" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case warning = portent.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 PORTENT mean?
PORTENT noun- Something that portends an event about to occur, especially an unfortunate or evil event; an omen.
- A portending; significance
- Something regarded as portentous; a marvel; prodigy.