One's knotted, restricting oxygen! (5)
I believe the answer is:
noose
'one's knotted restricting oxygen' is the definition.
I can't judge whether this definition defines the answer.
'one's knotted restricting oxygen' is the wordplay.
'knotted' is an anagram indicator.
'restricting' indicates putting letters inside.
'oxygen' becomes 'O' (O is the chemical symbol for oxygen).
'ones' anagrammed gives 'nose'.
'nose' going around 'o' is 'NOOSE'.
Can you help me to learn more?
(Other definitions for noose that I've seen before include "Catch" , "Hanging loop in rope" , "Bond" , "Loop formed by means of a slip knot" , "trap" .)