Little man with party piece (5)
I believe the answer is:
rondo
'piece' is the definition.
(type of musical composition)
'little man with party' is the wordplay.
'little man' becomes 'Ron' (short for Ronald).
'with' says to put letters next to each other.
'party' becomes 'do' (do is a kind of party).
'ron'+'do'='RONDO'
(Other definitions for rondo that I've seen before include "Repetitive musical form" , "Last movement of a sonata or concerto" , "Musical piece with a recurring theme" , "Music form with recurring theme" , "Musical work" .)