Polish guards caught old thieves lobbying leaders in country (8)
I believe the answer is:
scotland
'country' is the definition.
(Scotland is a country of the UK)
'polish guards caught old thieves lobbying leaders' is the wordplay.
'polish' becomes 'sand' (to polish or sand down).
'guards' is an insertion indicator (inserted letters are guarded).
'leaders' says to take the initial letters.
The initial letters of 'caught old thieves lobbying' is 'cotl'.
'sand' placed around 'cotl' is 'SCOTLAND'.
'in' is the link.
(Other definitions for scotland that I've seen before include "Strange clans dot this country" , "Country of Jock and Angus" , "It used to be called Caledonia" , "Land of clans and kilts" , "The thistle is its emblem" .)