Gangster, graduate, knight and saint (5)
I believe the answer is:
alban
'saint' is the definition.
(saint alban)
'gangster graduate knight' is the wordplay.
'gangster' becomes 'al' (Al Capone).
'graduate' becomes 'BA' (someone with a Bachelor of Arts degree).
'knight' becomes 'n' (chess abbreviation).
'al'+'ba'+'n'='ALBAN'
'and' is the link.
(Other definitions for alban that I've seen before include "First Christian martyr in England" , "Saintly type" , "-- Berg, composer" , "Saint born at Verulamium" , "Hertfordshire saint" .)