Anger beginning to ease aboard a ship (7)
I believe the answer is:
galleon
'a ship' is the definition.
(type of ship)
'anger beginning to ease aboard' is the wordplay.
'anger' becomes 'gall' (galling is a kind of angering).
'beginning to' says to take the initial letters.
'aboard' becomes 'on'.
The first letter of 'ease' is 'e'.
'gall'+'e'+'on'='GALLEON'
(Other definitions for galleon that I've seen before include "Historical warship with three or more masts" , "Old Spanish war-ship" , "Spanish treasure ship" , "One might sink" , "Large Spanish sailing ship of yore" .)