Encroach (8)
I believe the answer is:
trespass
'encroach' is the definition.
(I know that encroach is a more specific form of the action trespass)
This is all the clue.
(Other definitions for trespass that I've seen before include "Sin (archaic)" , "Go out of bounds" , "Enter someone else's property illegally" , "Enter land without permission" , "sin in the eyes of the church" .)