Heard bride-to-be will use a dye for decorative purposes! (5)
I believe the answer is:
henna
'heard bride-to-be' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
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 "Reddish brown dye used on hair" , "Cosmetic plant dye" , "Red-brown dye used for body decorations" , "Vegetable dye" , "Stainer" .)