Some massager — a serious rubber (6)
I believe the answer is:
eraser
'rubber' is the definition.
(rubber can mean an eraser)
'some massager a serious' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'ERASER' is hidden within 'massager a serious'.
(Other definitions for eraser that I've seen before include "A student's rubber, or the one who uses it" , "Implement to rub out" , "Rubbing-out device" , "A schoolboy's rubber" , "Implement for rubbing out" .)