Graduate's robes regularly get gibes (5)
I believe the answer is:
barbs
'gibes' is the definition.
('barb' can be a synonym of 'gibe')
'graduate's robes regularly' is the wordplay.
'graduate' becomes 'ba'.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'robes' are 'rbs'.
'ba'+'rbs'='BARBS'
'get' is the link.
(Other definitions for barbs that I've seen before include "Thorns or pointed remarks" , "Sedatives" , "Hurtful remarks" .)