Colouring agent used in kitchen, naturally (5)
I believe the answer is:
henna
'colouring agent' is the definition.
'in kitchen naturally' is the wordplay.
'in' says the answer is hidden in the clue.
'HENNA' is hidden within 'kitchen naturally'.
'used' is the link.
(Other definitions for henna that I've seen before include "Shrub used for reddish-brown dye" , "Reddish-brown plant dye" , "Reddish brown dye used on hair" , "Local colour" , "Red-brown dye used for body decorations" .)