Northbound vessel ships gold in island nation (5)
I believe the answer is:
nauru
'island nation' is the definition.
(Nauru is an island)
'northbound vessel ships gold' is the wordplay.
'northbound' says the letters should be written in reverse.
'vessel' becomes 'urn' (urn is a type of container).
'ships' means one lot of letters goes inside another (to ship can mean to carry or transport something).
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'urn' backwards is 'nru'.
'nru' going around 'au' is 'NAURU'.
'in' acts as a link.
(Other definitions for nauru that I've seen before include "Pacific coral island republic, once rich in phosphates" , "Small Pacific republic" , "Fairground carousel" , "[OCEANIA] location" , "Island country in Micronesia" .)