Nation of characters remarkable in their eloquence (4)
I believe the answer is:
eire
'nation' is the definition.
(Eire is an example)
'characters remarkable in their eloquence' is the wordplay.
'characters remarkable in' indicates a hidden word (remark can mean notice or observe).
'EIRE' can be found hidden inside 'their eloquence'.
'of' is the link.
(Other definitions for eire that I've seen before include "island" , "Breakaway state" , "Former name of the Irish Republic" , "Look for (something to happen)" , "Gaelic name for Republic of Ireland" .)