Concealed, I pay in bits for book of knowledge (13)
I believe the answer is:
encyclopaedia
'book of knowledge' is the definition.
'encyclopaedia' can be an answer for 'book' (encyclopaedia is a kind of book). I am not sure about the 'of knowledge' bit.
'concealed i pay in bits' is the wordplay.
'concealed i pay' anagrams to 'ENCYCLOPAEDIA'.
Though, I'm not clear how this is indicated.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for encyclopaedia that I've seen before include "Large reference book" , "Large reference work" , "Extensive reference work" , "Book covering whole range of knowledge" , "source of information" .)