Obstreperous, abrupt about university period before Easter (9)
I believe the answer is:
truculent
'obstreperous' is the definition.
('truculent' can be a synonym of 'obstreperous')
'abrupt about university period before easter' is the wordplay.
'abrupt' becomes 'curt' (I've seen this before).
'about' shows that the letters should be reversed in order.
'university' becomes 'u'.
'period before easter' becomes 'lent' (I've seen this before).
'curt' reversed gives 'truc'.
'truc'+'u'+'lent'='TRUCULENT'
(Other definitions for truculent that I've seen before include "Aggressively defiant" , "Surly" , "Defiantly aggressive" , "Quarrelsome" , "Defiant, rude" .)