It's wonderful to be good in sorting out a claim (7)
I believe the answer is:
magical
'it's wonderful' is the definition.
(I've seen this before)
'good in sorting out a claim' is the wordplay.
'good' becomes 'g' (abbreviation).
'in' is an insertion indicator.
'sorting out' indicates an anagram.
'a'+'claim'='aclaim'
'aclaim' is an anagram of 'maical'.
'g' put into 'maical' is 'MAGICAL'.
'to be' is the link.
(Other definitions for magical that I've seen before include "miraculous!" , "Enchanting or spell-binding" , "Charming" , "Bewitching" , "Enchanted" .)