Farmer (5)
'farmer' is the definition.
(agriculturist is a kind of farmer)
This is all the clue.
(Other definitions for agriculturist that I've seen before include "E.g. a farmer" , "Farming expert" .)
(Other definitions for cocky that I've seen before include "Conceited and arrogant like rooster" , "Bumptious, self-important" , "Cheekily conceited" , "Self-important, conceited" , "Full of oneself" .)