Ties up (7)
'ties up' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tethers that I've seen before include "moors" , "Ties up (horses)" , "Of animal, ties to prevent straying" , "Restrains with a rope" , "Fastens" .)
'ties up' is the definition.
('truss' can be a synonym of 'tie up')
This is all the clue.
(Another definition for trusses that I've seen is " Ties or binds with russets".)