Still, it’s regular (4)
I believe the answer is:
even
I believe this is a double definition.
'still' is the first definition.
('even' can be a synonym of 'still')
'regular' is the second definition.
('even' can be similar in meaning to 'regular')
'it's' is the link.
(Other definitions for even that I've seen before include "Steady or smooth" , "Flat, regular" , "no-win situation?" , "Pantomime" , "like six or twelve" .)