Some returned in carriage (4)
I believe the answer is:
trap
'carriage' is the definition.
(trap is a kind of carriage)
'some returned' is the wordplay.
'some' becomes 'part'.
'returned' says the letters should be written backwards.
'part' backwards is 'TRAP'.
'in' is the link.
(Other definitions for trap that I've seen before include "The Web" , "website?" , "Driver's obstacle" , "Control ball" , "Snaring device" .)