Do (7)
'do' is the definition.
(I know that serve is a more specific form of effect)
This is the entire clue.
(Other definitions for serve that I've seen before include "Put the tennis ball in play" , "Offer up" , "deal" , "Wait - start the game" , "Begin a tennis game" .)
'do' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for achieve that I've seen before include "Successfully conclude" , "Reach or accomplish" , "Manage to get" , "Skilfully bring about" , "Bring about by effort" .)