Clutch push rod oil seal AP0650320
Fitment - RSV 98-10, Tuono 02-10, Falco, Futura, Caponord ETV 1000
Aprilia OEM Clutch Push Rod Oil Seal, part number AP0650320, item 25 in the diagram.
Designed to prevent oil leaking past the clutch push rod. However with time it may become worn and brittle and will therefore need to be replaced if you notice any leaks. Fortunately, as this is a direct replacement, it will be an easy enough task to complete.