Dull college class (7)
I believe the answer is:
uniform
'dull' is the definition.
'college class' is the wordplay.
'college' becomes 'uni' (I've seen this in other clues).
'class' becomes 'form' (form class is a kind of class).
'uni'+'form'='UNIFORM'
(Other definitions for uniform that I've seen before include "army's gear" , "Unvarying as military dress" , "Regular - formal dress" , "Regular - soldier's dress" , "Clothing worn by members of a particular group" .)