Dull, monotonous (7)
I believe the answer is:
humdrum
I believe this is a double definition.
'dull' is the first definition.
(similar in meaning)
'monotonous' is the second definition.
(I know that monotonous can be written as humdrum)
(Other definitions for humdrum that I've seen before include "Common place" , "Boringly monotonous" , "Run-of-the-mill" , "Run of the mill" , "Mundane, commonplace" .)