Happily thorn is treated in kindness to man (12)
I believe the answer is:
philanthropy
'kindness to man' is the definition.
I can't judge whether this defines the answer.
'happily thorn is treated' is the wordplay.
'is treated' indicates anagramming the letters.
'happily'+'thorn'='happilythorn'
'happilythorn' is an anagram of 'PHILANTHROPY'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for philanthropy that I've seen before include "Generous deeds" , "Benevolence towards humanity" , "Humanitarianism" , "Benevolence to others" , "Practical benevolence" .)