Expel European supported by Cambridge university (4)
I believe the answer is:
emit
'expel' is the definition.
(emitting is a kind of expelling)
'european supported by cambridge university' is the wordplay.
'european' becomes 'e' (abbreviation e.g. EU).
'supported by' says to put letters next to each other (letters go below - in down clue).
'cambridge university' becomes 'mit' (Massachusetts Institute of Technology in Cambridge).
'e'+'mit'='EMIT'
(Other definitions for emit that I've seen before include "Give out (eg light)" , "Give out or pour forth" , "Exude" , "'Give out, light say (4)'" , "Give off, gas say" .)