Fantastic envoy rated when touring Norway occasionally (5,3,3,4)
I believe the answer is:
every now and then
'occasionally' is the definition.
(I've seen this before)
'fantastic envoy rated when touring norway' is the wordplay.
'fantastic' indicates anagramming the letters.
'touring' means one lot of letters goes inside another (touring can mean going round).
'norway' becomes 'n'.
'envoy'+'rated'+'when'='envoyratedwhen'
'envoyratedwhen' is an anagram of 'everynowadthen'.
'everynowadthen' enclosing 'n' is 'EVERY NOW AND THEN'.
(Other definitions for every now and then that I've seen before include "periodically" , "Not all of the time" , "at times" , "Occasionally" .)