Western hemisphere wonder extremely well developed (3,5)
I believe the answer is:
new world
'western hemisphere' is the definition.
('New World' can be a synonym of 'western hemisphere')
'wonder extremely well developed' is the wordplay.
'extremely' means to remove the middle letters.
'developed' indicates an anagram.
'well' with its middle taken out is 'wl'.
'wonder'+'wl'='wonderwl'
'wonderwl' with letters rearranged gives 'NEW WORLD'.
(Other definitions for new world that I've seen before include "America" , "The Americas, to the explorers" , "symphony?" , "Non-European" , "From the --- --- (Dvor++k)" .)