Prodigy (10)
'prodigy' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for wunderkind that I've seen before include "Child prodigy" , "Perhaps Mozart" , "Clever young person" , "One having early success" , "Extraordinary issue" .)
'prodigy' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for phenomenon that I've seen before include "Marvel?" , "Remarkable thing" , "Remarkable occurrence" , "Wonder" , "(Remarkable) happening" .)