Part of an open-door policy? (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
sesame
(Other definitions for sesame that I've seen before include "Small oval seeds yielding an edible oil" , "Seed or oil used in cooking" , "Seeds producing an edible oil" , "Ali Baba's opening command" , "said to be effective in opening spell" .)