Swimmer touring islands and one country (7)
I believe the answer is:
tunisia
'country' is the definition.
(Tunisia is an example)
'swimmer touring islands and one' is the wordplay.
'swimmer' becomes 'tuna' (tuna fish is a kind of fish).
'touring' means one lot of letters goes inside another (touring can mean going round).
'islands' becomes 'is' (i is an abbreviation for island).
'and' means one lot of letters go next to another.
'one' becomes 'i' (roman numeral).
'is'+'i'='isi'
'tuna' placed around 'isi' is 'TUNISIA'.
(Other definitions for tunisia that I've seen before include "Country between Algeria/Libya" , "Country in North Africa" , "Land" , "Country which contains the site of Carthage" , "Somewhere in North Africa" .)