Breed of dairy cattle (6)
(Other definitions for jersey that I've seen before include "Breed of cow; sweater" , "Clothing" , "Garment - cow - island" , "Pullover; an island" , "farm animal" .)
(Other definitions for guernsey that I've seen before include "off the Needles?" , "Neighbour of Jersey" , "Second largest Channel Island" , "Second-largest Channel Island" , "Channel isle" .)