Holy person drinks nothing -- I drink too much (3)
I believe the answer is:
sot
'i drink too much' is the definition.
(a sot is an alcoholic)
'holy person drinks nothing' is the wordplay.
'holy person' becomes 'st' (short for saint).
'drinks' is an insertion indicator.
'nothing' becomes 'o' (looks like zero - 0).
'st' going around 'o' is 'SOT'.
(Other definitions for sot that I've seen before include "One drinks" , "Toper" , "Boozer" , "Lush" , "One's often intoxicated" .)