Loop (5)
I believe the answer is:
noose
'loop' is the definition.
(I know that noose is a kind of loop)
This is all the clue.
(Other definitions for noose that I've seen before include "Halter loop" , "Hanging loop in rope" , "Hangman's running loop" , "Sliding loop in a lasso (5)" , "Snare, restraint" .)