Parenthetical Titles: (But She Can Rock And Roll)?

Questions

Myrtaceous tree of mostly Australian genus, such as the blue gum or ironbark, yielding a mecidinal oil from its leaves?

City-state and the largest port in Germany?

A method of voice production by male singers used to vocalise notes higher than their normal range?

Essential framework of any structure, outline consisting of bare essentials?

Designate as officially secret, and not for general disclosure?