Twist near end of knot to loosen (5)
I believe the answer is:
untie
'loosen' is the definition.
(thesaurus)
'twist near end of knot' is the wordplay.
'twist' says the letters should be written in reverse (I've seen 'twisted ' mean this).
'near end of' becomes 'nu' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'knot' becomes 'tie' (I've seen this before).
'nu' backwards is 'un'.
'un'+'tie'='UNTIE'
'to' is the link.
(Other definitions for untie that I've seen before include "Open a knot" , "Release (knots)" , "Release bindings or shoelaces" , "Separate" , "Remove fastenings from" .)