Local drink's consumed a great deal (7)
I believe the answer is:
bargain
'great deal' is the definition.
'local drink's consumed a' is the wordplay.
'local' becomes 'bar' (local can mean someone's local pub).
'drink' becomes 'gin' (gin is a kind of drink).
'consumed' is an insertion indicator.
'gin' going around 'a' is 'gain'.
'bar'+'gain'='BARGAIN'
(Other definitions for bargain that I've seen before include "Deal; cheap buy" , "Good buy" , "Favourable transaction" , "Barter, negotiate" , "Count on" .)