These speakers keep their topics to themselves (8)
I believe the answer is:
egotists
'themselves' is the definition.
Both the answer and definition are plural nouns.
Maybe there's an association between them I don't understand?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for egotists that I've seen before include "Self-centred self-seekers" , "Conceited and self-centered people" , "The selfish" , "They have an exaggerated sense of their own importance" , "People with exaggerated notions of their own importance" .)