The most common and most likely answer to this crossword clue is the 5 letter word EQUID
I've seen this crossword clue in The Times
E
Q
U
I
D
More clues leading to the result EQUID
Buddy explains!
The straight part
We know that "horse" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case horse = equid.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 EQUID mean?
EQUID noun- Any animal of the taxonomic family Equidae, including any equine (horse, zebra, ass, mule, etc.)