The most common and most likely answer to this crossword clue is the 11 letter word INTERRACIAL
I've seen this crossword clue in The Times
I
N
T
E
R
R
A
C
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A
L
More clues leading to the result INTERRACIAL
Buddy explains!

The straight part
We know that "affecting many people" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case affecting many people = interracial.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 INTERRACIAL mean?
INTERRACIAL adjective- Between or among two or more different races.