Marginal note revealing worry about appointment (7)
I believe the answer is:
apostil
'marginal note' is the definition.
(I've seen this in another clue)
'worry about appointment' is the wordplay.
'worry' becomes 'ail' (I've seen this before).
'about' is an insertion indicator.
'appointment' becomes 'post' (appointment to a job).
'ail' enclosing 'post' is 'APOSTIL'.
'revealing' is the link.
(Other definitions for apostil that I've seen before include "note to the side" , "note by text" , "marginal note" .)