Varnish ingredient (3)
I believe the answer is:
lac
'varnish ingredient' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lac that I've seen before include "Red resin secreted by insects" , "Ingredient of varnish" , "thousands from India" , "100,000 in rupees" , "insects secrete this" .)