Unique sort against an enemy turned King in with Duke (3,2,1,4)

'with duke' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'unique sort against an enemy turned king' is the wordplay.
'unique' becomes 'one' (synonyms).
'sort' becomes 'kind' (synonyms).
'against' means one lot of letters go next to another.
'an enemy turned king' becomes 'ofa' (I can't justify this - if you can you should believe this answer much more).
'kind' put after 'ofa' is 'ofakind'.
'one'+'ofakind'='ONE OF A KIND'

'in' is the link.

Can you help me to learn more?