Waiter can retain a lot of information (6)
I believe the answer is:
server
'waiter' is the definition.
(I know that waiter can be written as server)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for server that I've seen before include "Waiter or tennis player who puts ball into play" , "The one who sets the ball in play at tennis" , "Network-controlling computer" , "Waiter or computer facility" , "Description of tennis player setting ball in play" .)