Rope loop confused one so (5)
I believe the answer is:
noose
'rope loop' is the definition.
(I've seen this before)
'confused one so' is the wordplay.
'confused' indicates anagramming the letters.
'one'+'so'='oneso'
'oneso' with letters rearranged gives 'NOOSE'.
(Other definitions for noose that I've seen before include "it could endanger your life" , "Loop with sliding knot in a rope" , "Loop at the end of a rope" , "old execution method" , "Looped rope" .)