The most common and most likely answer to this crossword clue is the 10 letter word PESTILENCE
I've seen this crossword clue in The Times
P
E
S
T
I
L
E
N
C
E
More clues leading to the result PESTILENCE
- Splenetic European concocted serious complaint
- Case of pure Tamiflu primarily imported to quell epidemic
- Exercises calm about time for deadly epidemic
- European gripped by bad splenetic disease
- Splenetic European spreading disease
- Money covering up steps to produce plague
- A fatal epidemic? Change will involve certain steps
- Be quiet about temperature after exercise, seeing contagion
- Exercise secrecy about source of terrible disease
- Steps adopted by coppers in epidemic
Buddy explains!

The straight part
We know that "disease" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case disease = pestilence.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 PESTILENCE mean?
PESTILENCE noun- Any epidemic disease that is highly contagious, infectious, virulent and devastating.
- Anything harmful to morals or public order.