Small lump, e.g. of butter (4)
I believe the answer is:
knob
(Other definitions for knob that I've seen before include "Handle or dial" , "boss" , "Rounded handle" , "Ball" , "Small lump (of butter?)" .)
I believe the answer is:
knob
(Other definitions for knob that I've seen before include "Handle or dial" , "boss" , "Rounded handle" , "Ball" , "Small lump (of butter?)" .)