The most common and most likely answer to this crossword clue is the 5 letter word STEED
I've seen this crossword clue in Financial Times
S
T
E
E
D
More clues leading to the result STEED
- Pip covers head of timid horse
- Issue surrounding rear of draft horse
- Horse runs away in desert storm
- Avenger’s way to get river flowing backwards
- Children holding tail of draught horse
- Mount section ready for driving
- Horse from south ready for the off on course
- Horse cooked in casserole wife chucked out
- Horse in street starts to exasperate every driver
- Mount Everest’s old rocks — no place for new lovers
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 = steed.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 STEED mean?
STEED noun- A stallion, especially in the sense of mount.
- A bicycle.