Demolished grate to strangle thus! (7)
I believe the answer is:
garotte
'strangle thus' is the definition.
'garotte' can be an answer for 'strangle' (garotting is a kind of strangling). I'm not sure about the 'thus' bit.
'demolished grate to' is the wordplay.
'demolished' indicates anagramming the letters.
'grate'+'to'='grateto'
'grateto' with letters rearranged gives 'GAROTTE'.
Can you help me to learn more?
(Other definitions for garotte that I've seen before include "Facility to dispose of person" , "Strangle" , "Kill by strangulation" , "Spanish method of execution" , "throttle" .)