Restaurant workers making one go to get drinks (6)
I believe the answer is:
'drinks' is the definition.
(water is a drink)
I don't understand how the rest of the clue works.
(Other definitions for waters that I've seen before include "What may be taken at a spa" , "(Of the mouth) salivates" , "Irrigates" , "Muddy - - (blues singer)" , "floods" .)