Ring in snout looks deadly (5)
I believe the answer is:
noose
'ring' is the definition.
(I have seen 'Ring of rope' mean 'noose' so perhaps 'ring' could also mean 'noose')
'in snout looks deadly' is the wordplay.
'in' is an insertion indicator.
'snout' becomes 'nose' (informal term for nose).
'looks deadly' becomes 'o' (I can't justify this - if you can you should believe this answer much more).
'nose' enclosing 'o' is 'NOOSE'.
Can you help me to learn more?
(Other definitions for noose that I've seen before include "it could endanger your life" , "Catcher" , "marriage, for a laugh" , "Loop of cord" , "Loop formed by means of a slip knot" .)