Caesar's farewell
I believe the answer is:
vale
'caesar's farewell' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for vale that I've seen before include "'''Sweet ... of Avoca, how calm could I rest'' (Moore) (4)'" , "Valley" , "Glen; goodbye!" , "Trough between ridges" , "Maida -, N. London area; farewell (archaic)" .)