Graduate is a loud man but so regular! (7)
I believe the answer is:
alumnus
'graduate' is the definition.
(I know that graduate can be written as alumnus)
'a loud man but so regular' is the wordplay.
'regular' means one should take alternating letters.
'loud'+'man'+'but'+'so'='loudmanbutso'
The alternate letters of 'loudmanbutso' are 'lumnus'.
'a'+'lumnus'='ALUMNUS'
'is' acts as a link.
(Other definitions for alumnus that I've seen before include "Past pupil" , "(US) college graduate" , "School or college graduate" , "Former pupil or student" , "Former college pupil" .)