The most common and most likely answer to this crossword clue is the 9 letter word NURSERIES
I've seen this crossword clue in The Times
N
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R
S
E
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More clues leading to the result NURSERIES
Buddy explains!

The straight part
We know that "races" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case races = nurseries.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 NURSERIES mean?
NURSERIES noun- A place where nursing or the raising of children is carried on.
- A place where anything is fostered and growth promoted.
- Something which educates and nurtures.
- Short for nursery cannon.
- Someone or something that is nursed; a nursling.
- The act of nursing or rearing.