The most common and most likely answer to this crossword clue is the 10 letter word INHUMANITY
I've seen this crossword clue in The Guardian
I
N
H
U
M
A
N
I
T
Y
More clues leading to the result INHUMANITY
Buddy explains!

The straight part
We know that "Cruelty/Cruelty" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cruelty/cruelty = inhumanity.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 INHUMANITY mean?
INHUMANITY noun- The lack of compassion.
- An inhuman act.