Some used yellow henna (3)
I believe the answer is:
dye
'henna' is the definition.
(I've seen this in another clue)
'some used yellow' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'DYE' can be found hidden inside 'used yellow'.
(Other definitions for dye that I've seen before include "Colouring; sounds like fade" , "Colouring matter" , "Staining material" , "Colouring material" , "Colourant" .)