Dump reward (3)
I believe the answer is:
tip
This clue is a double definition.
'dump' is the first definition.
(as in a rubbish tip)
'reward' is the second definition.
(I have seen 'tiny reward' mean 'tip' so perhaps 'reward' could also mean 'tip')
(Other definitions for tip that I've seen before include "Give the likely winner for gratuity" , "Warning" , "present!" , "Hint about a horse" , "Helpful suggestion" .)