Chart out cure — principally tobacco is a killer (9)
I believe the answer is:
cutthroat
'killer' is the definition.
(cutthroat is a kind of killer)
'chart out cure principally tobacco' is the wordplay.
'cure' indicates anagramming the letters (I've seen 'cured' mean this).
'principally' indicates taking the first letters.
The first letter of 'tobacco' is 't'.
'chart'+'out'='chartout'
'chartout' with letters rearranged gives 'cutthroa'.
'cutthroa'+'t'='CUTTHROAT'
'is a' acts as a link.
(Other definitions for cutthroat that I've seen before include "Murderer - fiercely competitive" , "Ruthless in competition" , "violent criminal!" , "Ruthless, intense" , "Fiercely competitive -- type of razor" .)