Still divisible by two (4)
I believe the answer is:
even
This clue is a double definition.
'still' is the first definition.
(I know that still can be written as even)
'divisible by two' is the second definition.
(I've seen this before)
(Other definitions for even that I've seen before include "Level, calm" , "Plumb" , "Still - quits" , "Smooth, uniform in quality" , "Regular - smooth" .)