Fish — is one netted in that country? (7)
I believe the answer is:
tunisia
'country?' is the definition.
(Tunisia is an example)
'fish is one netted in' is the wordplay.
'fish' becomes 'tuna' (tuna is a kind of fish**).
'one' becomes 'i' (Roman numeral).
'netted in' indicates putting letters inside.
'is'+'i'='isi'
'tuna' going around 'isi' is 'TUNISIA'.
'that' acts as a link.
(Other definitions for tunisia that I've seen before include "As Inuit visits there in North Africa" , "Republic in northwestern Africa" , "African republic on the Mediterranean coast" , "Suit Ian to be in North African country" , "Country where Carthage is found" .)