Part of Hungarian song (4)
I believe the answer is:
aria
'song' is the definition.
(piece of music in an opera)
'part of hungarian' is the wordplay.
'part of' says the answer is hidden in the clue.
'ARIA' can be found hidden inside 'hungarian'.
(Other definitions for aria that I've seen before include "Operatic number" , "Operatic song" , "Operatic part" , "Puccini item" , "Operatic solo performance" .)