Pain -- managed amazingly without New Zealand! (7)
I believe the answer is:
myalgia
'pain' is the definition.
(I know that myalgia is a type of myalgia)
'managed amazingly without new zealand' is the wordplay.
'managed' is an anagram indicator.
'without' suggests deleting specific letters.
'new zealand' becomes 'nz'.
'amazingly' with 'nz' taken away is 'amaigly'.
'amaigly' is an anagram of 'MYALGIA'.
(Other definitions for myalgia that I've seen before include "painful muscle condition" , "Muscular pain" , "Muscle pain" , "sort of pain!" .)