The most common and most likely answer to this crossword clue is the 8 letter word STAGGERS
I've seen this crossword clue in The Sunday Telegraph
S
T
A
G
G
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S
More clues leading to the result STAGGERS
- Horse disease is shocking
- Tsar’s egg addled, leading to complaint
- People putting on plays including grand shocks
- Shocks skinhead graffiti artists
- Beastly condition beginning to grate in veterans
- Stock complaint from canonised cricket commentator?
- Disease in animals causes amazement
- Condition of livestock causes amazement
- Comical gagster succeeded with rolls
- Veterans maintaining good condition in horses
Buddy explains!

The straight part
We know that "condition in horses" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case condition in horses = staggers.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 STAGGERS mean?
STAGGERS noun- An unsteady movement of the body in walking or standing as if one were about to fall; a reeling motion
- A disease of horses and other animals, attended by reeling, unsteady gait or sudden falling
- Bewilderment; perplexity.
- The spacing out of various actions over time.
- The difference in circumference between the left and right tires on a racing vehicle. It is used on oval tracks to make the car turn better in the corners.
- The horizontal positioning of a biplane, triplane, or multiplane's wings in relation to one another.
- Sway unsteadily, reel, or totter.
- Doubt, waver, be shocked.
- Have multiple groups doing the same thing in a uniform fashion, but starting at different, evenly-spaced, times or places (attested from 1856).
- Any of various diseases of animals that affects the nervous system, characterized by a lack of control of the limbs