Graduates in vessel (5)
I believe the answer is:
basin
'vessel' is the definition.
(basin is a kind of vessel)
'graduates in' is the wordplay.
'graduates' becomes 'BAs' (people with Bachelor of Arts degrees).
'bas'+'in'='BASIN'
(Other definitions for basin that I've seen before include "Region drained by a river" , "Large bowl" , "Round open dish for water" , "Bowl-shaped vessel" , "Round open dish for washing" .)