Origin of deadly green extract (4)
I believe the answer is:
draw
'extract' is the definition.
(I've seen this before)
'origin of deadly green' is the wordplay.
'origin of' says to take the initial letters.
'green' becomes 'raw' ('raw' can be a synonym of 'green'**).
The initial letter of 'deadly' is 'd'.
'd'+'raw'='DRAW'
(Other definitions for draw that I've seen before include "Drag" , "Attract; sketch" , "Pull; take in (breath)" , "attractive thing" , "Design" .)