Grain from lab produced with rye (6)
I believe the answer is:
barley
'grain' is the definition.
(I know that barley is a type of grain)
'lab produced with rye' is the wordplay.
'produced with' is an anagram indicator.
'lab' mixed up with 'rye' makes 'BARLEY'.
'from' is the link.
(Other definitions for barley that I've seen before include "Hardy cereal" , "Grain used in making beer" , "Type of cereal" , "A hardy grass" , "Bristly cereal" .)