Man taking one on for the country (6)
I believe the answer is:
nation
'the country' is the definition.
(synonyms)
'man taking one on' is the wordplay.
'man' becomes 'nat' ().
'taking' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'nat'+'i'+'on'='NATION'
'for' is the link.
(Other definitions for nation that I've seen before include "Body of people under one government" , "People of common culture or descent" , "People of a state" , "A federation of tribes, as Native Americans say" , "Race" .)