Clue: To make up story about king, head of Númenor: this author did! (7)
Answer: TOLKIEN
Explanation: Definition: this author did!
A charade of TOLKIE, an envelope ('about') of K ('king') in TO LIE ('to make up story'); plus N ('head of **N**úmenor'), with an extended definition. Note that this clue has what I refer to as an extended definition, or a semi-&lit, in that 'this author did' does not contribute to the wordplay. 25D is a true &lit, in that the entire clue may be read as wordplay or definition.