Where one may find today's crossword, or a collection of previous ones? (9)
I believe the answer is:
paperback
'collection of previous ones?' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'where one may find today's crossword or a' is the wordplay.
I cannot quite see how this works, but
'one' could be 'a' (a thing is one thing) and 'a' is found within the answer.
'a' could be 'per' (eg 'one a day' means 'one per day') and 'per' is present in 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 paperback that I've seen before include "Publication" , "Book with soft cover" .)