Mine includes mid-evening drink (4)
I believe the answer is:
pint
'drink' is the definition.
(thesaurus)
'mine includes mid-evening' is the wordplay.
'mine' becomes 'pit' (down the pit).
'includes' indicates putting letters inside.
'mid' means to look at the middle letters.
The middle of 'evening' is 'n'.
'pit' placed around 'n' is 'PINT'.
(Other definitions for pint that I've seen before include "Imperial measure of capacity" , "The working man's drink measure" , "Glass of beer (colloq.)" , "Unit of beer" , "Standard measure of beer or milk" .)