The most common and most likely answer to this crossword clue is the 2 plus 2 plus 1 plus 6 letter word GO ON A BENDER
G
O
O
N
A
B
E
N
D
E
R
Buddy explains!
The straight part
We know that "drink a lot of alcohol" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case drink a lot of alcohol = go on a bender.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.