Country round lake (4)
I believe the answer is:
eire
'country' is the definition.
(Eire is an example)
'round lake' is the wordplay.
'round' says the letters should be written in reverse.
'lake' becomes 'erie' (Lake Erie is one of the Canadian/US 'Great Lakes').
'erie' back-to-front is 'EIRE'.
(Other definitions for eire that I've seen before include "Southern Ireland" , "Irish name for Ireland" , "island" , "Former name for the Republic of Ireland" , "Gaelic name for Republic of Ireland" .)