Level, flat (4)
I believe the answer is:
even
I believe this clue is a double definition.
'level' is the first definition.
(I know that level can be written as even)
'flat' is the second definition.
(level)
(Other definitions for even that I've seen before include "Commensurate" , "draw" , "happening to take time off?" , "Regular - smooth" , "Flat - yet" .)