Remain at Oxford maybe and don't retire (4,2)
I believe the answer is:
stay up
'don't retire' is the definition.
(as in staying awake instead of retiring to bed)
'remain at oxford maybe' is the wordplay.
'remain' becomes 'stay' (synonyms).
'at oxford maybe' becomes 'up' ('up' can mean at university).
'stay'+'up'='STAY UP'
'and' acts as a link.
(Other definitions for stay up that I've seen before include "Keep late hours; avoid relegation" , "postpone retirement" , "Decide not to retire" , "Don't retire" , "Don't go to bed - don't be relegated" .)