Add page to one set of religious books, and go after expression of uncertainty (10)
I believe the answer is:
interleave
'add page to one set of religious books' is the definition.
I can't judge whether this definition defines the answer.
'go after expression of uncertainty' is the wordplay.
'go' becomes 'leave' (go can mean to depart or leave).
'after' says to put letters next to each other.
'expression of uncertainty' becomes 'inter' (I can't explain this - if you can you should give a lot more credence to this answer).
'leave' put after 'inter' is 'INTERLEAVE'.
'and' is the link.
Can you help me to learn more?
(Other definitions for interleave that I've seen before include "Insert between (book) pages" , "put in blank pages" .)