Turn to part of the book to show what has been leaked (7)
I believe the answer is:
seepage
'turn' is the definition.
The answer and definition can be both related to natural events as well as being singular nouns.
Perhaps there's an association between them I don't understand?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for seepage that I've seen before include "Slowly leaking flow" , "narrow escape?" , "liquid having soaked through" , "Slow fluid loss" , "slow escape" .)