Tormentor (6)
(Other definitions for abuser that I've seen before include "one who uses bad language" , "Person who over-indulges in, say, drugs or drink" , "He takes undue advantage" , "One mistreating another" , "One who reviles or a misuser of drugs" .)
'tormentor' is the definition.
(I know that tormentor can be written as teaser)
This is the entire clue.
(Other definitions for teaser that I've seen before include "Tricky question; intriguing preliminary advert" , "Difficult problem concerning Easter" , "Introduction to arouse curiosity" , "Tricky question; intriguing ad" , "Puzzling question or gentle goader" .)
'tormentor' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sadist that I've seen before include "An amalgam, made up of two or more parts" , "One who takes pleasure in cruelty" , "One who enjoys cruelty" , "Tormentor" , "One who delights in cruelty" .)