Rope is on order for murderer (8)
I believe the answer is:
poisoner
'murderer' is the definition.
(I know that poisoner is a type of murderer)
'rope is on order' is the wordplay.
'order' indicates anagramming the letters.
'rope'+'is'+'on'='ropeison'
'ropeison' is an anagram of 'POISONER'.
'for' acts as a link.
(Other definitions for poisoner that I've seen before include "Person who uses chemicals to kill" , "Killer using a toxic substance" , "Dr Crippen, perhaps" , "One who administers the fatal chemical." , "Eg, Dr Crippen" .)