Number-cruncher who doesn't return to library? (10)
I believe the answer is:
bookkeeper
'number-cruncher who doesn't return to library?' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
This is the entire clue.
Can you help me to learn more?
(Other definitions for bookkeeper that I've seen before include "Accounts official" , "accountant" , "Business occupation" , "person responsible for financial oversight" , "who works to maintain balance" .)