Is a bit of a risk at Oxford (4)
I believe the answer is:
isis
'oxford' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'is a bit of a risk' is the wordplay.
'a bit of' suggests taking the first letters.
'a risk' becomes 'sis' (I can't justify this - if you can you should believe this answer much more).
The first letter of 'is' is 'i'.
'i'+'sis'='ISIS'
'at' acts as a link.
Can you help me to learn more?
(Other definitions for isis that I've seen before include "Oxford's second eight" , "Revered figure" , "Old Egyptian fertility goddess" , "academic stream?" , "divinity" .)