Note from doctor following case of malpractice (4)
I believe the answer is:
memo
'note' is the definition.
(memo is a kind of note)
'doctor following case of malpractice' is the wordplay.
'doctor' becomes 'mo' (medical officer**).
'following' says to put letters next to each other.
'case of' says to hollow out the word (remove centre letters) (outsides of).
'malpractice' with its middle removed is 'me'.
'mo' after 'me' is 'MEMO'.
'from' is the link.
(Other definitions for memo that I've seen before include "Brief note, usually between co-workers" , "Note written as a reminder" , "Written business message, in short" , "Reminder (abbr)" , "Businesslike message" .)