Vessel going to an island city (5)
I believe the answer is:
tunis
'city' is the definition.
(Tunis is an example)
'vessel going to an island' is the wordplay.
'vessel' becomes 'tun' (tun is a kind of vessel**).
'going to' is a charade indicator (letters next to each other).
'an island' becomes 'is'.
'tun'+'is'='TUNIS'
(Other definitions for tunis that I've seen before include "N African port" , "Mediterranean capital and port" , "Carthage lies near this N. African city" , "North African location" , "North African city" .)