US thinker, being uninitiated, bored by setter (7)
I believe the answer is:
emerson
'uninitiated bored by setter' is the definition.
The definition suggests a singular noun which matches the answer.
'us thinker' is the wordplay.
I cannot really see how this works, but
'us' could be 'me' ('us' can mean 'mean' in some UK dialects) and 'me' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'being' is the link.
Can you help me to learn more?
(Other definitions for emerson that I've seen before include "American writer, 1803-82" , "American author, 1803-82" , "Ralph Waldo --, US author" , "Ralph Waldo ......., 19th century American transcendentalist" , "--, Lake and Palmer, rock group" .)