Article by both upset about book one, a fantasy novel (3,6)
I believe the answer is:
the hobbit
'a fantasy novel' is the definition.
(I know that The Hobbit is a fantasy novel)
'article by both upset about book one' is the wordplay.
'article' becomes 'the' (the definite article in English).
'by both upset about book one' becomes 'hobbit' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'the'+'hobbit'='THE HOBBIT'
Can you help me to learn more?
(Other definitions for the hobbit that I've seen before include "fantasy" , "Novel" , "saga" .)