The most common and most likely answer to this crossword clue is the 6 letter word BLIGHT
I've seen this crossword clue in The Times
B
L
I
G
H
T
More clues leading to the result BLIGHT
- Disease is an irritating thing, no hesitation
- Plant disease bad at first, not serious after
- Disease that can follow planning
- Minimum of blasphemy, mild curse
- Ruin bishop’s day
- Bishop has amusing setback
- Curse a follower with brilliance
- Fungus evident in bay round lake
- Damage front of bedside lamp
- British settle historical Irish problem
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 = blight.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 BLIGHT mean?
BLIGHT noun- Any of many plant diseases causing damage to, or the death of, leaves, fruit or other parts.
- The bacterium, virus or fungus that causes such a condition.
- (by extension) Anything that impedes growth or development or spoils any other aspect of life.
- To affect with blight; to blast; to prevent the growth and fertility of.
- To suffer blight.
- To spoil or ruin (something).