Rotter requiring small drink (5)
I believe the answer is:
swine
'rotter' is the definition.
(both can mean a horrible person)
'small drink' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'drink' becomes 'wine' (wine is an alcoholic drink).
's'+'wine'='SWINE'
'requiring' is the link.
(Other definitions for swine that I've seen before include "Pig; unpleasant person" , "Pig, pigs" , "See 9" , "cad" , "Nasty people" .)