Understanding nation re-elected lunatic (7,8)
I believe the answer is:
entente cordiale
'understanding' is the definition.
(entente cordiale is a kind of understanding)
'nation re-elected lunatic' is the wordplay.
'lunatic' indicates anagramming the letters.
'nation'+'re'+'elected'='nationreelected'
'nationreelected' with letters rearranged gives 'ENTENTE CORDIALE'.
(Other definitions for entente cordiale that I've seen before include "Understanding" , "Agreement" .)