### Clue: Lively parts from singer unknown in South Island (7)
### Answer: SCHERZI 
 ### Explanation: Definition: Lively parts
 [ CHER(pop singer) + Z(in mathematics, a symbol for an unknown variable) **contained in**(in) [ S(abbrev. for "south") + I(abbrev. for "island") ].
Defn: … in a musical piece.