Wait on (6)
'wait on' is the definition.
(to wait on someone is to serve them)
This is all the clue.
(Other definitions for serve that I've seen before include "Be useful to" , "Work for, be of use to" , "Act as waiter" , "deal" , "Attend; start to play tennis" .)
'wait on' is the definition.
(eg a servant attends or waits on someone)
This is the entire clue.
(Other definitions for attend that I've seen before include "notice" , "put in an appearance" , "Show up" , "Be present at (an event)" , "take heed" .)