The most common and most likely answer to this crossword clue is the 8 letter word PRODROME
P
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Buddy explains!
The straight part
We know that "sign of coming disease" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sign of coming disease = prodrome.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 PRODROME mean?
PRODROME noun- A precursor or harbinger; also a warning event.
- An introductory or preliminary book or treatise.
- An early symptom warning of the onset of a disease.
- Prodromous.