Clue: Auf wiedersehen, literally? (7,2,6)
Answer: GOODBYE TO BERLIN
Explanation: Definition: literally?
A book by Christopher Isherwood – is the definition "literally"=>'in literature, e.g. a novel'?
 GOODBYE TO BERLIN could be read as 'crosswordese' instructions to translate 'goodbye' into German, giving "Auf wiedersehen"