Legislation is effective (4)
I believe the answer is:
acts
This clue is a double definition.
'legislation' is the first definition.
(I've seen this in another clue)
'is effective' is the second definition.
(I've seen this before)
(Other definitions for acts that I've seen before include "Cast (anag) - performs" , "performers for revue, say?" , "No head for details in book" , "Turns" , "Behaves or plays" .)