Instal new leader... (6)
I believe the answer is:
stalin
'leader' is the definition.
(Stalin is an example)
'instal new' is the wordplay.
'new' is an anagram indicator.
'instal' with letters rearranged gives 'STALIN'.
(Other definitions for stalin that I've seen before include "Former Soviet leader" , "Soviet dictator, d. 1953" , "Dreaded dictator among Latins" , "Former Georgian theology student, d. 1953" , "Mass-murderer" .)