Decline to enter a dubious agreement (7,8)
I believe the answer is:
entente cordiale
'agreement' is the definition.
(entente cordiale is a kind of agreement)
'decline to enter a dubious' is the wordplay.
'dubious' indicates anagramming the letters.
'decline'+'to'+'enter'+'a'='declinetoentera'
'declinetoentera' is an anagram of 'ENTENTE CORDIALE'.
(Other definitions for entente cordiale that I've seen before include "Agreement" , "Understanding" .)