Dull, yellowish-brown (5)
I believe the answer is:
khaki
I believe this clue is a double definition.
'dull' is the first definition.
(khaki is a dull colour)
'yellowish-brown' is the second definition.
(thesaurus)
(Other definitions for khaki that I've seen before include "Yellowish brown (used by military)" , "Military uniform's cloth" , "Military fabric" , "Drab military colour" , "Olive-drab colour" .)