Legendary creature in college - something afoot! (7)
I believe the answer is:
unicorn
'legendary creature' is the definition.
'unicorn' can be an answer for 'creature' (I've seen this before). I'm not sure about the 'legendary' bit.
'college something afoot' is the wordplay.
'college' becomes 'uni' (I've seen this in other clues).
'something afoot' becomes 'corn' (I am not sure about this - if you are sure you should believe this answer much more).
'uni'+'corn'='UNICORN'
'in' is the link.
Can you help me to learn more?
(Other definitions for unicorn that I've seen before include "Fabulous one-horned animal" , "Imaginary, horned horse-like creature" , "Fabulous horned animal" , "Mythical animal with one horn" , "that's fabulous" .)