University cricketer upset, being out (4)
I believe the answer is:
tabu
'being out' is the definition.
('tabu' can be a synonym of 'out')
'university cricketer upset' is the wordplay.
'university' becomes 'u' (abbreviation for university).
'cricketer' becomes 'bat' (I've seen this before).
'upset' is a reversal indicator.
'u'+'bat'='ubat'
'ubat' in reverse letter order is 'TABU'.
(Other definitions for tabu that I've seen before include "Social prohibition" , "Forbidden (Alt sp.)" , "beyond the pale" , "delicate matter?" , "Disapproved of" .)