Member, one's slow to pass law (9)
I believe the answer is:
Here is my best explanation:
'pass law' is the definition.
(I've seen this before)
'member one's slow' is the subsidiary indication.
'member' becomes 'leg' (leg is a kind of member**).
'one's' becomes 'is' ('I' can be a synonym of 'one').
'slow' becomes 'late' (I've seen this in other clues).
'to' is the link.
(Other definitions for legislate that I've seen before include "what members do?", "Pass law", "Make rules", "what parliament must do", "Make a ruling", "Pass laws", "Pass through the house", "Establish rules", "For what governments do" and "Enact laws".)