Top place to go on a ship (4)
I believe the answer is:
head
I believe this is a double definition.
'top' is the first definition.
(thesaurus)
'place to go on a ship' is the second definition.
(term for a toilet on a ship)
(Other definitions for head that I've seen before include "River or stream source" , "Cranium" , "Leader; promontory" , "Lead - school principal" , "Promontory; foam" .)