The most common and most likely answer to this crossword clue is the 5 letter word THREE
I've seen this crossword clue in The Times
T
H
R
E
E
More clues leading to the result THREE
- Trinity right within you
- Fairly good hotel in a street in resort, close to pier
- We help in their shambolic call to vote
- The vet yearned to reform equestrian contest
- Its entrants are bound to stagger, cheered in old country
- Article about Religious Education Cardinal's produced
- Rugby players — 75% of them?
- Harry Potter hurt nine, which drivers sometimes can do
- Religious class absorbed by the Trinity
- Fifty percent of members bound to participate in this event?
Buddy explains!

The straight part
We know that "equestrian contest" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case equestrian contest = three.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 THREE mean?
THREE noun- The digit/figure 3.
- Anything measuring three units, as length.
- A person who is three years old.
- The playing card featuring three pips.
- A numerical value after two and before four. Represented in Arabic digits as 3; this many dots (•••).
- Describing a set or group with three elements.
- A goal or other means of scoring worth three points.
- A three-point shot; a basket made from beyond the three-point line.
- A three-point landing; an airplane landing in which all three wheels touch the ground simultaneously.
- A deer or other animal whose antlers feature three points or tines.