Loop ring through snout (5)
I believe the answer is:
noose
'loop' is the definition.
(I know that noose is a type of loop)
'ring through snout' is the wordplay.
'ring' becomes 'o' (O is the shape of a ring).
'through' is an insertion indicator (inserted letters go through the word).
'snout' becomes 'nose' (informal term for nose).
'o' going into 'nose' is 'NOOSE'.
(Other definitions for noose that I've seen before include "Hangman's halter" , "Hangman's running loop" , "Catcher" , "Loop - snare" , "it could endanger your life" .)