Crossword Genius

Its use may be said to be dying (5)

Ross

I believe the answer is:

henna

I'm a little stuck... Click here to teach me more about this clue!

'be dying' is the definition.
The definition and answer can be both substances as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for henna that I've seen before include "A shrub, its red dye" , "hair colouring" , "Red-brown dye used for body decorations" , "Reddish dye for hair etc" , "natural colour?" .)

I've seen this clue in the Evening Standard.
Want a hint initially instead of a full solution? Install my app