One serving tea to make crust we hear (3)
I believe the answer is:
urn
'one serving tea to make crust we hear' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
This is all the clue.
Can you help me to learn more?
(Other definitions for urn that I've seen before include "Vessel for making hot drinks" , "Container for tea or ashes" , "Large pot for coffee or tea" , "Without cost; last word of Tempest" , "A large vase as for human ashes" .)