Old-fashioned, missing last appointment (4)
I believe the answer is:
date
'appointment' is the definition.
(I know that appointment can be written as date)
'old-fashioned missing last' is the wordplay.
'old fashioned' becomes 'dated' (I've seen this before).
'missing last' means to remove the last letter.
'dated' with its last letter removed is 'DATE'.
(Other definitions for date that I've seen before include "Sweet fruit with a long woody seed" , "Court" , "Go out with" , "Oval fruit" , "Tropical fruit" .)