Buzz from America is a thick-skinned sort (6)
I believe the answer is:
callus
'a thick-skinned sort' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'buzz from america' is the wordplay.
'buzz from' becomes 'call' (I can't justify this - if you can you should give a lot more credence to this answer).
'america' becomes 'us' (abbreviation for the United States).
'call'+'us'='CALLUS'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for callus that I've seen before include "Corn" , "Skin problem" , "A sore point" , "Thickened skin patch" , "Area of hard skin" .)