College fashion is military clothing (7)
I believe the answer is:
uniform
'military clothing' is the definition.
(I've seen this before)
'college fashion' is the wordplay.
'college' becomes 'uni' (short for university).
'fashion' becomes 'form' (both can mean to shape something for a purpose).
'uni'+'form'='UNIFORM'
'is' acts as a link.
(Other definitions for uniform that I've seen before include "Distinctive clothing worn by a group" , "distinctive clothes" , "Military tunic" , "Consistent, unvarying" , "reluctant pupils may be forced to wear it" .)