Machine part for carriage (7)
I believe the answer is:
bearing
This clue is a double definition.
'machine part' is the first definition.
(I know that bearing is a type of machine part)
'for carriage' is the second definition.
(synonyms)
(Other definitions for bearing that I've seen before include "Relevance, way of moving" , "Small sphere" , "Attitude - pivot - reference" , "circular form?" , "Compass point" .)