Emperor replacing his allies with ease (5,8)
I believe the answer is:
haile selassie
'emperor' is the definition.
(Haile Selassie is an example)
'replacing his allies with ease' is the wordplay.
'replacing' is an anagram indicator (re-placing: placing the letters again).
'with' means one lot of letters go next to another.
'his'+'allies'='hisallies'
'hisallies' after 'ease' is 'easehisallies'.
'easehisallies' anagrammed gives 'HAILE SELASSIE'.
(Other definitions for haile selassie that I've seen before include "Leader revered in Ethiopia" , "African emperor" , "Emperor of Ethiopia, deposed 1974" , "Ethiopian emperor" , "The Rastafarian Messiah" .)