Set free; loosen (5)
I believe the answer is:
untie
This clue is a double definition.
'set free' is the first definition.
(I've seen this before)
'loosen' is the second definition.
(I know that loosen can be written as untie)
(Other definitions for untie that I've seen before include "resolve" , "Detach" , "Free from restraining bonds or ropes" , "Loose bonds" , "Remove ropes, unfasten" .)