A leak, you understand, to the paper (7)
I believe the answer is:
seepage
'a leak' is the definition.
(I've seen this before)
'understand to the paper' is the wordplay.
'understand' becomes 'see' (synonyms).
'to the paper' becomes 'page' (a page is a sheet of paper).
'see'+'page'='SEEPAGE'
'you' is the link.
(Other definitions for seepage that I've seen before include "running out slowly" , "Loss from slow leak" , "Slowly leaking flow" , "Percolation" , "liquid having soaked through" .)