Finally, dispatchers finish post (4)
I believe the answer is:
send
'post' is the definition.
(I know that post can be written as send)
'finally dispatchers finish' is the wordplay.
'finally' indicates one should take the final letters.
'finish' becomes 'end' (synonyms).
The final letter of 'dispatchers' is 's'.
's'+'end'='SEND'
(Other definitions for send that I've seen before include "Sentence to a prison term" , "Transmit; post" , "Dispatch by post" , "Cause to go for" , "Transmit (message)" .)