Big shot in rare sort of child's play (2-7)
I believe the answer is:
no-brainer
'child's play' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'big shot in rare sort' is the wordplay.
'big shot' becomes 'nob' (I can't explain this - if you can you should believe this answer much more).
'sort' indicates anagramming the letters.
'in'+'rare'='inrare'
'inrare' is an anagram of 'rainer'.
'nob'+'rainer'='NO-BRAINER'
'of' is the link.
Can you help me to learn more?
(Other definitions for no-brainer that I've seen before include "Something involving little or no mental effort" , "That which must be done, obviously" , "Something needing little mental effort" , "Something requiring little or no mental effort" , "An easy decision" .)