Tedious, dreary (4)
I believe the answer is:
dull
I believe this clue is a double definition.
'tedious' is the first definition.
(similar in meaning)
'dreary' is the second definition.
(similar in meaning)
(Other definitions for dull that I've seen before include "Drab" , "Lusterless or uninteresting" , "Boring - not sunny" , "Uninspiring" , "Matt; overcast" .)