Periodical by graduate is hot stuff! (5)
I believe the answer is:
magma
'hot stuff' is the definition.
(I've seen this before)
'periodical by graduate' is the wordplay.
'periodical' becomes 'mag' (abbreviation for magazine).
'by' is a charade indicator (letters next to each other).
'graduate' becomes 'ma' (abbreviation for Master of Arts).
'mag'+'ma'='MAGMA'
'is' is the link.
(Other definitions for magma that I've seen before include "Molten or pasty rock" , "hot stuff" , "Lava" , "crust's content" , "That's hot!" .)