Harness (4)
(Other definitions for yoke that I've seen before include "Bond of servitude" , "Eg, pair of draught oxen" , "Part of garment" , "Burdensome restraint or oppression" , "Frame joining draught oxen at the necks" .)
'harness' is the definition.
(I know that harness can be written as rein)
This is all the clue.
(Other definitions for rein that I've seen before include "Curb" , "Controlling strap" , "Leather used for control in horse-riding" , "Restriction" , "Restraint; strap attached to horse's bit" .)