Country's prison with a district attorney (6)
I believe the answer is:
canada
'country's' is the definition.
(Canada is an example)
'prison with a district attorney' is the wordplay.
'prison' becomes 'can' (the can is American slang for prison).
'with' says to put letters next to each other.
'district attorney' becomes 'D.A.' (abbreviation).
'can'+'a'+'da'='CANADA'
(Other definitions for canada that I've seen before include "Commonwealth country" , "Queen Elizabeth is it's head of state" , "Second-largest country in the world by area" , "Montreal's country" , "N American nation" .)