Government concerned with eg uprising, arresting one million (6)
I believe the answer is:
regime
'government' is the definition.
(synonyms)
'concerned with eg uprising arresting one million' is the wordplay.
'concerned with' becomes 're' ('re' means regarding or about).
'uprising' is an anagram indicator.
'arresting' is an insertion indicator.
'one million' becomes 'im' (resembles 1m).
'eg' is an anagram of 'ge'.
'ge' going around 'im' is 'gime'.
're'+'gime'='REGIME'
(Other definitions for regime that I've seen before include "Command" , "Ruling system" , "Method or system of government" , "Form of rule" , "Emigre (anag.)" .)