College class’s prescribed clothing (7)
I believe the answer is:
uniform
'prescribed clothing' is the definition.
(eg clothing required for a job)
'college class's' is the wordplay.
'college' becomes 'uni' (short for university).
'class' becomes 'form class' (form class is a kind of class).
'uni'+'form'='UNIFORM'
(Other definitions for uniform that I've seen before include "Military tunic" , "Not varying, like army clothes" , "Regular - formal dress" , "Distinctive outfit" , "Unvarying as military dress" .)