A lark's in rambling country (3,5)
I believe the answer is:
sri lanka
'country' is the definition.
(Sri Lanka is an example)
'a lark's in rambling' is the wordplay.
'rambling' indicates an anagram.
'a'+'larks'+'in'='alarksin'
'alarksin' with letters rearranged gives 'SRI LANKA'.
(Other definitions for sri lanka that I've seen before include "Country in 4" , ""The teardrop of India"" , "Ceylon since 1972" , "'Formerly Ceylon (3,5)'" , "It used to be called Ceylon" .)