Nuncio led astray finds seventh heaven (5,4)
I believe the answer is:
cloud nine
'seventh heaven' is the definition.
(synonyms)
'nuncio led astray' is the wordplay.
'astray' indicates anagramming the letters.
'nuncio'+'led'='nuncioled'
'nuncioled' with letters rearranged gives 'CLOUD-NINE'.
'finds' is the link.
(Other definitions for cloud nine that I've seen before include "On this, one is extremely happy" , "Situation of great elation" , "If you're on this, you're extremely happy" , "On which one is blissfully happy" .)