Extra component of a machine (5,4)

I believe the answer is:
spare part
(Other definitions for spare part that I've seen before include "something put in machine?" , "Replacement component" , "Type of surgery" , "Extra component for machine" .)
I believe the answer is:
spare part
(Other definitions for spare part that I've seen before include "something put in machine?" , "Replacement component" , "Type of surgery" , "Extra component for machine" .)