Rope one so released (5)
I believe the answer is:
noose
'rope' is the definition.
(noose is a kind of rope)
'one so released' is the wordplay.
'released' is an anagram indicator (letters released from their original order).
'one'+'so'='oneso'
'oneso' anagrammed gives 'NOOSE'.
(Other definitions for noose that I've seen before include "Circular loop" , "Loop in a lariat" , "Device for capital punishment" , "Hangman's running loop" , "Rope around the neck" .)