The "thee" of "of thee I sing" (7)
I believe the answer is:
america
'the thee of of thee i sing' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for america that I've seen before include "Land of the free and home of the brave?" , "Curious camera I take to the continent" , "Camera I found in the continent" , "The superpower" , "The US" .)