Old book, mostly outraged, about nothing at all (8)
I believe the answer is:
oblivion
'old' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'book mostly outraged about nothing at all' is the wordplay.
I cannot really see how this works, but
'book' could be 'b' (abbreviation for book) and 'b' is located in the answer.
'about' could be 'on' (as in a book 'on' a certain topic) and 'on' is found within the answer.
'nothing' could be 'o' (O resembles 0) and 'o' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for oblivion that I've seen before include "Insensibility" , "Obscurity" , "ignorance" , "lack of fame" , "Unconsciousness - nothingness" .)