Kindly feeling expressed by happy legatee (8)
I believe the answer is:
goodwill
'happy legatee' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'kindly feeling' is the wordplay.
'kindly' becomes 'good' (similar in meaning).
'feeling' becomes 'will' (I can't explain this - if you can you should believe this answer much more).
'good'+'will'='GOODWILL'
'expressed by' acts as a link.
Can you help me to learn more?
(Other definitions for goodwill that I've seen before include "friendly attitude" , "Benevolence" , "intangible asset" , "Benevolent feeling - business asset" , "compassion" .)