Last word (1920s) (9)
(Other definitions for abyssinia that I've seen before include "Former nation" , "country in Africa" , "Former name of northeast African country" , "former African state" , "Ethiopia's former name" .)
(Other definitions for the that I've seen before include "and 24 Down: Similar things" , "See 10 Across" , "That particular one" , "Born - - - - - - - - (carol)" , "Over - - moon" .)
'last word' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for finis that I've seen before include "End (of book or film)" , "conclusion!" .)