Is excessively enthusiastic to get at the drink? (4,9)

'the drink?' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'is excessively enthusiastic to get' is the wordplay.
I cannot really understand how this works, but
'excessively' could be 'over' and 'over' is located in the answer.
'get' could be 'go' (synonyms) and 'go' is found in the answer.
This may be the basis of the clue (or it may be nonsense).

'at' acts as a link.

Can you help me to learn more?