Natural hair dye (5)
I believe the answer is:
henna
'natural hair dye' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for henna that I've seen before include "natural colour?" , "Reddish dye for hair etc" , "hair colour?" , "Beauty aid" , "Shrub used for reddish-brown dye" .)