Priest’s vacuous perception grasped slice from a book? (5,3)

I believe the answer is:

paper cut

I'm a little stuck... Click here to teach me more about this clue!

'slice from a book?' is the definition.
(I've seen this in another clue)

I don't understand the rest of the clue.

I've seen this clue in the Sydney Morning Herald.

Want a hint initially instead of a full solution? Install my app