One interacted busily with the French for pact with them (7,8)
I believe the answer is:
entente cordiale
'one' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for entente cordiale that I've seen before include "Agreement" , "Understanding" .)