Sit on note including papers (4)
I believe the answer is:
ride
'sit' is the definition.
(I know that sit can be written as ride)
'note including papers' is the wordplay.
'note' becomes 're' (as in do-re-mi).
'including' means one lot of letters goes inside another.
'papers' becomes 'ID' (short for identification papers).
're' enclosing 'id' is 'RIDE'.
'on' is the link.
(Other definitions for ride that I've seen before include "Fairground entertainment" , "Eg, roundabout or roller-coaster, path for horses" , "Travel on the back of animal" , "Take journey" , "Travel in or be carried on" .)