Note about hospital department, as a reminder (7)
I believe the answer is:
memento
'a reminder' is the definition.
(I know that memento is a type of reminder)
'note about hospital department' is the wordplay.
'note' becomes 'memo' (memo is a kind of note).
'about' indicates putting letters inside.
'hospital department' becomes 'ENT' (abbreviation for Ear, Nose and Throat department).
'memo' enclosing 'ent' is 'MEMENTO'.
'as' acts as a link.
(Other definitions for memento that I've seen before include "might be kept for sentimental reasons" , "This reminds" , "Souvenir, reminder of past event" , "Something kept" , "Object kept as a souvenir" .)