Finish off Chablis just opened during meal (7)
I believe the answer is:
scupper
'finish off chablis' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'opened during meal' is the wordplay.
'opened' becomes 'c' (I am not sure about this - if you are sure you should believe this answer much more).
'during' is an insertion indicator.
'meal' becomes 'supper' (supper is a kind of meal).
'c' placed within 'supper' is 'SCUPPER'.
'just' acts as a link.
Can you help me to learn more?
(Other definitions for scupper that I've seen before include "Ruin, put paid to" , "foil" , "Deliberately sink (oneself)" , "Thwart" , "Hole for draining" .)