The most common and most likely answer to this crossword clue is the 8 letter word PELLAGRA
I've seen this crossword clue in Independent
P
E
L
L
A
G
R
A
More clues leading to the result PELLAGRA
- Disease in quiet Indian city — measure must be introduced
- Itching to see Indian city with unlimited enchantments
- Disease from vitamin deficiency: everyone returned to tuck into confection of grape
- Vegetable eating wholly brought about King George’s disease
- Short period without sun and Indian city gets disease
- Para-legal lost an article, mutated, and got a disease
- “No second entrance” — tourist city's complaint
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 = pellagra.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 PELLAGRA mean?
PELLAGRA noun- A disease characterised by skin lesions and mental confusion, primarily caused by a niacin deficiency.