Visually blah (4)
I believe the answer is:
drab
'visually blah' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for drab that I've seen before include "Drearily dull; slattern" , "Cheerless, colourless" , "Shabby; a slattern (arch.)" , "Lacklustre" , "Dull, uninteresting" .)