Student's flipping cheek at university (5)
I believe the answer is:
pupil
'student's' is the definition.
('pupil' can be a synonym of 'student')
'flipping cheek at university' is the wordplay.
'flipping' is a reversal indicator.
'cheek' becomes 'lip' (both can mean insolence or rudeness).
'at university' becomes 'up'.
'lip'+'up'='lipup'
'lipup' back-to-front is 'PUPIL'.
(Other definitions for pupil that I've seen before include "that shrinks from brightness" , "One being taught" , "A student at school or eye part" , "Centre of iris, in the eye" , "part of my anatomy" .)