Deal with enemy finally to effect this? (6)
I believe the answer is:
treaty
This might be a double definition.
'deal' is the first definition.
(I know that treaty is a type of deal)
'enemy finally to effect this?' is the second definition.
The definition suggests a singular noun which matches the answer.
'with' is the link.
Can you help me to learn more?
(Other definitions for treaty that I've seen before include "something of Rome or Versailles?" , "International agreement" , "settlement" , "Contract between states" , "convention?" .)