Enthusiastic diner has the wrong end of goblet (5)
I believe the answer is:
eager
'enthusiastic' is the definition.
(similar in meaning)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for eager that I've seen before include "Enthusiastic, raring to go" , "Keen (as a beaver?)" , "Swiss mountain" , "Enthusiastic, full of desire" , "Alert and active type?" .)