Most of group returned in carriage (4)
I believe the answer is:
trap
'carriage' is the definition.
(trap is a kind of carriage)
'most of group returned' is the wordplay.
'most of' means to remove the last letter.
'group' becomes 'party'.
'returned' says the letters should be written in reverse.
'party' with its final letter taken off is 'part'.
'part' backwards is 'TRAP'.
'in' acts as a link.
(Other definitions for trap that I've seen before include "Light horse-drawn carriage" , "Light carriage - it's sometimes sprung!" , "Ambush" , "Light carriage; ensnare" , "Snare; pony carriage" .)