Grain, local, the French buy finally (6)
I believe the answer is:
barley
'grain' is the definition.
(barley is a kind of grain)
'local the french buy finally' is the wordplay.
'local' becomes 'bar' (local can mean someone's local pub).
'the french' becomes 'le' ('the' in French).
'finally' suggests the final letters.
The last letter of 'buy' is 'y'.
'bar'+'le'+'y'='BARLEY'
(Other definitions for barley that I've seen before include "A cereal plant or its grain" , "Cereal used in brewing" , "A cereal plant with bearded spikes" , "Bristly cereal" , "Cereal grass" .)