Enter property illegally (8)
I believe the answer is:
trespass
'enter property illegally' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for trespass that I've seen before include "Go out of bounds" , "Commit a sin -- spa's rest (anag)" , "Enter someone else's property illegally" , "Illegally entering" , "Unlawful entry to someone's property" .)