Wine kept in extension finally made mine (8)
I believe the answer is:
excavate
'mine' is the definition.
(thesaurus)
'wine kept in extension finally' is the wordplay.
I cannot really see how this works, but
'wine' could be 'cava' (I have seen 'Spanish wine ' mean 'cava' so perhaps 'wine' could also mean 'cava') and 'cava' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'made' acts as a link.
Can you help me to learn more?
(Other definitions for excavate that I've seen before include "mine" , "With spade" , "Dig a hole" , "Dig out material from the ground" , "Quarry" .)