The kindness of people (8)
I believe the answer is:
humanity
'the kindness' is the definition.
(thesaurus)
'people' is the wordplay.
I cannot quite see how this works, but
'people' could be 'man' (I've seen this in other clues) and 'man' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for humanity that I've seen before include "Quality of our race?" , "Merciful nature" , "Kindness (of people in general)" , "Benevolence -- compassion" , "Nature of mankind" .)