Dish made from a sample of waste-water (4)
I believe the answer is:
stew
'dish' is the definition.
(stew is a kind of dish)
'a sample of waste-water' is the wordplay.
'a sample of' says the answer is hidden in the clue (I've seen this in other clues).
'STEW' is hidden in the letters of 'waste water'.
'made from' is the link.
(Other definitions for stew that I've seen before include "Cook; worry" , "State of mental agitation (informal)" , "Cook (in one's own juices?)" , "Cook - hash" , "State of anxiety; dish" .)