Guard dispatched before brief communist uprising (8)
I believe the answer is:
sentinel
'guard' is the definition.
(sentinel is a kind of guard)
'dispatched before brief communist uprising' is the wordplay.
'dispatched before' becomes 'sent' (I've seen this before. I am not sure about the 'before' bit.**).
'brief' means to remove the last letter.
'communist' becomes 'lenin' (Lenin is an example).
'uprising' says the letters should be written in reverse.
'lenin' with its last letter removed is 'leni'.
'leni' written backwards gives 'inel'.
'sent'+'inel'='SENTINEL'
(Other definitions for sentinel that I've seen before include "One watching" , "Soldier keeping watch" , "Guard whose job is to stand and keep watch" , "Soldier who stands and keeps watch" , "Watcher on guard" .)