The most common and most likely answer to this crossword clue is the 6 letter word TRIBES
T
R
I
B
E
S
More clues leading to the result TRIBES
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 = tribes.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 TRIBES mean?
TRIBES noun- A socially, ethnically, or politically cohesive group of people.
- A society larger than a band but smaller than a state.
- A group of apes who live and work together.
- A hierarchal rank between family and genus.
- The collective noun for various animals.
- (stock breeding) A family of animals descended from some particular female progenitor, through the female line.