Drinking cup (6)
(Other definitions for beaker that I've seen before include "Flatbottomed drinking cup" , "Glass container in a laboratory" , "Glass vessel" , "Plastic drinking vessel" , "Open glass, straight with lip, used in laboratory" .)
'drinking cup' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for goblet that I've seen before include "Stemmed drinking glass" , "Drinking-glass with stem and foot" , "Chalice" , "Ornate glass" , "Bowl-shaped drinking vessel" .)