Loop with a running knot (5)
I believe the answer is:
noose
'loop with a running knot' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for noose that I've seen before include "Loop in a rope made with a slip knot" , "Loop formed by means of a slip knot" , "it could endanger your life" , "Loop at the end of a rope" , "Hanging material" .)