The most common and most likely answer to this crossword clue is the 10 letter word GENEROSITY
I've seen this crossword clue in The Daily Telegraph
G
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N
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R
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More clues leading to the result GENEROSITY
Buddy explains!

The straight part
We know that "kindness" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case kindness = generosity.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 GENEROSITY mean?
GENEROSITY noun- The trait of being willing to donate money, time or resources.
- A generous act.
- The trait of being abundant, more than adequate.
- Good breeding; nobility of stock.