Impinge (8)
I believe the answer is:
encroach
'impinge' is the definition.
(synonyms)
This is all the clue.
(Other definitions for encroach that I've seen before include "Go past a normal limit" , "'Trespass, infringe (8)'" , "Intrude on someone's territory or time" , "Advance beyond the usual limit" , "Impinge, infringe" .)