Butters

3 clues
Tops, as toast
Flatters, with 'up'
Uses flattery on (with "up")
Similar answers:
Abaters
Abetters
Aborters
Abut
Abutment
Abutments
Abuton
Abuts
Abutsat
Abutson
Abutsupon
Abuttal
Abutted
Abutter
Abutting
Acadapters
Accepters
Accouters
Acquitters
Acters