Speak about a king, leader of Abyssinians for so long (8)

I believe the answer is:

sayonara

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'so long' is the definition.
('sayonara' can be a synonym of 'so long')

'speak about a king leader of abyssinians' is the wordplay.
'speak about' becomes 'sayon' (I can't justify this - if you can you should believe this answer much more).
'a king' becomes 'ar' (I've seen this in other clues).
'leader of' indicates taking the first letters.
The initial letter of 'abyssinians' is 'a'.
'sayon'+'ar'+'a'='SAYONARA'

'for' is the link.

Can you help me to learn more?

(Other definitions for sayonara that I've seen before include "Japanese goodbye" , "Goodbye (Jap.)" , "Goodbye or farewell in Japan" , "So long" , "Japanese valediction" .)

I've seen this clue in The Telegraph.

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