Waiter's reward (3)
I believe the answer is:
tip
'waiter's reward' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tip that I've seen before include "lots of rubbish" , "Hint about a horse" , "expected by those who wait" , "Gratuity or light touch" , "End; piece of advice" .)