Look over part of document showing what's leaking (7)
I believe the answer is:
seepage
'leaking' is the definition.
(I've seen this before)
'look over part of document showing' is the wordplay.
'look' becomes 'see'.
'over' says to put letters next to each other.
'part of document showing' becomes 'page' (I am not sure about this - if you are sure you should believe this answer much more).
'see'+'page'='SEEPAGE'
'what's' is the link.
Can you help me to learn more?
(Other definitions for seepage that I've seen before include "Slow leaking flow" , "slow escape" , "Percolation" , "Ooze" , "Slowly leaking flow" .)