Host who knows all the answers
I believe the answer is:
quizmaster
'host' is the definition.
(quizmaster is a kind of host)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for quizmaster that I've seen before include "Panel-game host" , "Person asking the questions" , "Presenter asking the questions" , "Asker of (trivia) questions" , "or on TV perhaps" .)