Carriage enclosure in Irish county (8)
I believe the answer is:
clarence
'carriage' is the definition.
(thesaurus)
'enclosure in irish county' is the wordplay.
'enclosure' becomes 'enc'.
'in' indicates putting letters inside.
'irish county' becomes 'clare'.
'enc' put inside 'clare' is 'CLARENCE'.
(Other definitions for clarence that I've seen before include "Duke drowned in a butt of Malmsey" , "Horse-drawn carriage; man's name" , "He was supposedly drowned in malmsey" , "boy" .)