Rope (off) (6)
I believe the answer is:
cordon
'rope off' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for cordon that I've seen before include "Chain (of police)" , "Protective ring" , "'Line, of police say, around an area to prevent entry (6)'" , "In cooking, . . . . . . bleu is excellent" , "Rope barrier" .)