Code word for Y (6)
I believe the answer is:
yankee
'code word for y' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for yankee that I've seen before include "North American soldier in civil war" , "Y in radio alphabet" , "Union soldier in the American Civil War" , "Informal American, a doodle dandy" , "A bet; US Federal soldier" .)