Oxford college or one the Spanish added (5)
I believe the answer is:
oriel
'oxford college' is the definition.
(Oriel College, Oxford)
'or one the spanish added' is the wordplay.
'one' becomes 'i' (Roman numeral).
'the spanish' becomes 'el' ('the' in Spanish).
'added' says to put letters next to each other.
'or'+'i'+'el'='ORIEL'
(Other definitions for oriel that I've seen before include "Large snake" , "place to study at Oxford" , "Protruding window" , "English college" , "One could look through this" .)