Herb; reddish-brown (6)
I believe the answer is:
sorrel
I believe this clue is a double definition.
'herb' is the first definition.
(I know that sorrel is a type of tea)
'reddish-brown' is the second definition.
(I've seen this before)
(Other definitions for sorrel that I've seen before include "Edible plant, horse of light reddish-brown coat" , "It provides flavour" , "Reddish brown horse or sharp-tasting herb" , "Horse of reddish-brown colour" , "Weed - colour of horse" .)