Poisoner: one of ten on the way in the distance (9)
I believe the answer is:
mistletoe
'poisoner' is the definition.
'one of ten on the way in the distance' is the wordplay.
'one of ten' becomes 'toe'.
'on' means one lot of letters go next to another.
'the way in the distance' becomes 'mistle' (I can't explain this - if you can you should believe this answer much more).
'toe' after 'mistle' is 'MISTLETOE'.
(Other definitions for mistletoe that I've seen before include "it may get you a few smackers" , "Evergreen plant" , "tempting a smack?" , "Plant with white berries, facilitates kissing" , "Valley of the -, best seller by Jacqueline Susann" .)