Said one's goodbyes in Split (8)
I believe the answer is:
departed
'said one's goodbyes' is the definition.
The answer and definition can be both to do with fundamental existence as well as being past participle verbs.
Perhaps there's an association between them I don't understand?
'in split' is the wordplay.
'in' becomes 'de' (I can't justify this - if you can you should give a lot more credence to this answer).
'split' becomes 'parted' (I've seen this before).
'de'+'parted'='DEPARTED'
Can you help me to learn more?
(Other definitions for departed that I've seen before include "completely breathless" , "Left -- late" , "Left, went away" , "Quit" , "Dead; set off" .)