Maple-syrup sources (4)
I believe the answer is:
saps
'maple-syrup sources' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for saps that I've seen before include "Pass around foolish people" , "Drains energy from" , "mugs" , "Weakens, undermines" , "Weakens, deprives of energy" .)