Man's clue, written cryptically, for powerful nation's government (5,3)
I believe the answer is:
uncle sam
'powerful nation's government' is the definition.
(Uncle Sam can mean the US government)
'man's clue written cryptically' is the wordplay.
'written cryptically' is an anagram indicator.
'mans'+'clue'='mansclue'
'mansclue' is an anagram of 'UNCLE SAM'.
'for' acts as a link.
(Other definitions for uncle sam that I've seen before include "The United States" , "Federal government" , "USA personified" , "Statesman" , "Iconic male relative of USA" .)