Reddish-brown hair dye (5)
I believe the answer is:
henna
'reddish-brown hair dye' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for henna that I've seen before include "Reddish dye for hair etc" , "Shrub used for cosmetic colouring" , "Red-brown plant dye" , "Natural hair dye" , "Vegetable dye" .)