Dressing county (4)
I believe the answer is:
mayo
This clue is a double definition.
'dressing' is the first definition.
(mayo is a condiment or dressing)
'county' is the second definition.
(county of Ireland)
(Other definitions for mayo that I've seen before include "Irish county (county town, Castlebar)" , "Saucy thing" , "Irish county - sauce (abbr)" , "Cold, creamy sauce (abbr)" , "County of Western Eire" .)