Plant grown for seeds (6)
I believe the answer is:
sesame
'plant grown for seeds' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sesame that I've seen before include "Plant grown for its seeds" , "Plant with oil-rich seeds" , "Seed or oil used in cooking" , "which magically opens" , "Small oval seeds yielding an edible oil" .)