Fool in Kansas occasionally (3)
I believe the answer is:
ass
'fool' is the definition.
(both can mean a stupid person)
'kansas occasionally' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
The alternating letters of 'kansas' are 'ASS'.
'in' acts as a link.
(Other definitions for ass that I've seen before include "One easily had" , "Dolt" , "transporter" , "Quadruped; fool" , "Clinton's behind" .)