Killing two fools with one country (13)
I believe the answer is:
assassination
'killing' is the definition.
(I know that assassination is a type of murder)
'two fools with one country' is the wordplay.
'two fools' can mean two replacements for 'fool'.
'fool' becomes 'ass' (both can mean a stupid person).
'fool' becomes 'ass' (both can mean a stupid person).
'with' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'country' becomes 'nation' (synonyms).
'ass'+'ass'+'i'+'nation'='ASSASSINATION'
(Other definitions for assassination that I've seen before include "Politically-inspired murder" , "Merciful, lenient" , "execution" , "Political killing" , "(Eg, political) murder" .)