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 "Enact laws", "Pass laws", "Make or enact laws" and "Pass law".)