Drain noodle juice (3)
I believe the answer is:
sap
I believe this clue is a triple definition!
'drain' is the first definition.
(sap can mean to suck or drain)
'noodle' is the second definition.
(both can mean a foolish person)
'juice' is the third definition.
(juice from a plant)
(Other definitions for sap that I've seen before include "Moisture in tree or informal dunce" , "Exhaust" , "Drain - vital fluid" , "Plant's fluid" , "Enervate" .)