Graduate is back - large man (5)
I believe the answer is:
basil
'man' is the definition.
(I've seen this before)
'graduate is back large' is the wordplay.
'graduate' becomes 'BA' (someone with a Bachelor of Arts degree).
'back' is a reversal indicator.
'large' becomes 'L' (eg in clothes sizes).
'is' in reverse letter order is 'si'.
'ba'+'si'+'l'='BASIL'
(Other definitions for basil that I've seen before include "Seasoning" , "serially chaotic character" , "Herb; forename" , "Herb - boy's name" , "Aromatic herb with purplish-green leaves" .)