Discontinue misdirecting the post (4)
I believe the answer is:
stop
'discontinue' is the definition.
(I know that discontinue is a more specific form of stop)
'misdirecting the post' is the wordplay.
'misdirecting' is an anagram indicator (I've seen 'misdirected' mean this (I've seen this in other clues)).
'post' anagrammed gives 'STOP'.
(Other definitions for stop that I've seen before include "Pause - prevent" , "Arrest" , "End - period" , "cut out" , "Go no further" .)