Dull color (4)
I believe the answer is:
gray
'dull color' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gray that I've seen before include "In America, dull" , "Author of ballad opera" , "English poet" , "An Anatomist; an Elegist" , "Midway between white and black" .)