Drinker very tipsy at the beginning (3)
I believe the answer is:
sot
'drinker' is the definition.
(I know that sot is a type of drinker)
'very tipsy at the beginning' is the wordplay.
'very' becomes 'so' (both can mean 'extremely').
'at the beginning' suggests taking the first letters.
The first letter of 'tipsy' is 't'.
'so'+'t'='SOT'
(Other definitions for sot that I've seen before include "Toper" , "Boozer" , "Habitual drunkard" , "Habitual drinker" , "Lush" .)