Hapless victim (3)
I believe the answer is:
sap
'hapless victim' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sap that I've seen before include "The juice in trees" , "Juice; energy" , "Vigour, energy" , "Weaken; tree fluid" , "trench used in siege" .)