Rope that’s not long now twisted with energy (5)
I believe the answer is:
noose
'rope' is the definition.
(noose is a kind of rope)
'not long now twisted with energy' is the wordplay.
I cannot really understand how this works, but
'not' could be 'no' (negative) and 'no' is found within the answer.
'energy' could be 'e' (physics symbol as in E=mc2) and 'e' is present in the answer.
The remaining letters 'os' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'that's' is the link.
Can you help me to learn more?
(Other definitions for noose that I've seen before include "Hangman's knot" , "Hangman's equipment" , "Catch" , "Halter loop" , "Hangman's running loop" .)