The most common and most likely answer to this crossword clue is the 8 letter word SHINGLES
I've seen this crossword clue in The Guardian
S
H
I
N
G
L
E
S
More clues leading to the result SHINGLES
- Disease affected legs, lower part first
- 24 Complaint of individuals getting out of hospital
- Singular sort of English disease
- Complaint from unmarried people about husband
- Disease of bony part of leg, leg broken by son
- Building materials for a painful inflammatory disease
- Unmarried sister initially consumes a pinch of hashish for herpes zoster
- Tinder users, say, receiving husband’s complaint
- Singular sort of English affliction
Buddy explains!

The straight part
We know that "Complaint" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case complaint = shingles.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 SHINGLES mean?
SHINGLES noun- Herpes zoster, caused by Human herpes virus 3, in genus Varicellovirus.
- A small, thin piece of building material, often with one end thicker than the other, for laying in overlapping rows as a covering for the roof or sides of a building.
- A rectangular piece of steel obtained by means of a shingling process involving hammering of puddled steel.
- A small signboard designating a professional office; this may be both a physical signboard or a metaphoric term for a small production company (a production shingle).
- A punitive strap such as a belt.
- (by extension) Any paddle used for corporal punishment.
- Small, smooth pebbles, as found on a beach.