America can, employing army, win (6)
I believe the answer is:
attain
'win' is the definition.
(thesaurus)
'america can employing army' is the wordplay.
'america' becomes 'a' (common abbreviation - e.g. in organisation names).
'can' becomes 'tin' ('tin' can be a synonym of 'can').
'employing' indicates putting letters inside.
'army' becomes 'ta' (abbreviation for Territorial Army).
'tin' enclosing 'ta' is 'ttain'.
'a'+'ttain'='ATTAIN'
(Other definitions for attain that I've seen before include "Fulfil" , "Arrive at or achieve" , "Reach or accomplish" , "Reach a goal" , "Reach (a specified age)" .)