One who's enthusiastic to drink loads, ignoring sign of disapproval (6)
I believe the answer is:
zealot
'one who's enthusiastic' is the definition.
'drink loads ignoring sign of disapproval' is the wordplay.
I cannot really understand how this works, but
'loads' could be 'alot' and 'alot' is found within the answer.
This explanation may well be incorrect...
'to' acts as a link.
(Other definitions for zealot that I've seen before include "A fanatic or over-enthusiastic person" , "A fanatic or extremist" , "Fervent advocate" , "Fervent, perhaps militant, proponent" , "Fanatic person, much too enthusiastic" .)