Ties the rest in knots (7)
I believe the answer is:
tethers
'ties' is the definition.
(I've seen this in another clue)
'the rest in knots' is the wordplay.
'in knots' is an anagram indicator (I've seen this in other clues).
'the'+'rest'='therest'
'therest' is an anagram of 'TETHERS'.
(Other definitions for tethers that I've seen before include "moors" , "Of animal, ties to prevent straying" , "Restrains with a rope" , "Ties up (horses)" , "Fastens" .)