Graduate, after swim, to behold a certificate (7)
I believe the answer is:
diploma
'a certificate' is the definition.
(academic certificate)
'graduate after swim to behold' is the wordplay.
'graduate' becomes 'MA' (abbreviation for Master of Arts).
'after' is a charade indicator (letters next to each other).
'swim' becomes 'dip' (dip can mean a brief swim).
'to behold' becomes 'lo' (archaic exclamation meaning 'look!').
'dip'+'lo'='diplo'
'ma' put after 'diplo' is 'DIPLOMA'.
(Other definitions for diploma that I've seen before include "Certificate awarded by college for educational attainment" , "Document conferring honour" , "What a student seeks" , "Academic certificate" , "documentation" .)