Level, regular (4)
I believe the answer is:
even
This clue is a double definition.
'level' is the first definition.
(synonyms)
'regular' is the second definition.
(similar in meaning)
(Other definitions for even that I've seen before include "notwithstanding" , "of consistent quality" , "happening to take time off?" , "(Of a number) divisible by 2" , "on level terms" .)