Notice leaf dripping (7)
I believe the answer is:
seepage
'dripping' is the definition.
(thesaurus)
'notice leaf' is the wordplay.
'notice' becomes 'see' (I've seen this before).
'leaf' becomes 'page' (page is a kind of leaf).
'see'+'page'='SEEPAGE'
(Other definitions for seepage that I've seen before include "problem with tank" , "Slowly leaking flow" , "Slow leakage" , "liquid having soaked through" , "Percolation" .)