Vessel with graduates aboard (5)
I believe the answer is:
basin
'vessel' is the definition.
(I know that basin is a type of vessel)
'with graduates aboard' is the wordplay.
'with' means one lot of letters go next to another.
'graduates' becomes 'BAs' (people with Bachelor of Arts degrees).
'aboard' becomes 'in' (I've seen this in other clues).
'bas' put next to 'in' is 'BASIN'.
(Other definitions for basin that I've seen before include "Depression in the earth's surface" , "Area drained by a river" , "dock, maybe" , "Stoup" , "container" .)