Juice to some extent poisonous apparently (3)
I believe the answer is:
sap
'juice' is the definition.
(juice from a plant)
'to some extent poisonous apparently' is the wordplay.
'to some extent' indicates the answer is hidden within the clue (I've seen 'extent of' mean this (I've seen this in other clues)).
'SAP' is hidden within 'poisonous apparently'.
(Other definitions for sap that I've seen before include "Plant's fluid" , "Juice; energy" , "trench used in siege" , "Deplete, drain of resources" , "Exhaust" .)