Send after? (4)
I believe the answer is:
post
This clue is a double definition.
'send' is the first definition.
(to send in the post)
'after?' is the second definition.
(prefix meaning after, eg post-war)
(Other definitions for post that I've seen before include "Leave message online" , "Pole - position" , "Position; mail" , "Send; job" , "Send via the mail" .)