Half of the world’s leading historians make the ambassador break up the crumbling empires (10)
I believe the answer is:
hemisphere
'half' is the definition.
(thesaurus)
'the world's leading historians make the ambassador break up the crumbling empires' is the wordplay.
I cannot quite understand how this works, but
'ambassador' could be 'he' (His or Her Excellency) and 'he' is found within the answer.
'up' could be 'is' (I've seen this in other clues) and 'is' is located in the answer.
This explanation may well be incorrect...
'of' acts as a link.
Can you help me to learn more?
(Other definitions for hemisphere that I've seen before include "covers half the world" , "part of the world" , "See 6" , "Global division" , "Half of the earth" .)