One digs up wine drunk by e.g. retired politician, mostly (9)

'one digs' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's a link between them I don't understand?

'up wine drunk by e g retired politician mostly' is the wordplay.
I cannot quite see how this works, but
'wine' could be 'cava' (type of Spanish wine) and 'cava' is found in the answer.
'by' could be 'x' (2 by 4 is 2 x 4) and 'x' is found within the answer.
'e' is found in the answer.
'retired' could be 'r' (abbreviation) and 'r' is present in the answer.
The remaining letters 'to' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?