Idiot, mature, going round university in temper (7)
I believe the answer is:
assuage
'temper' is the definition.
(thesaurus)
'idiot mature going round university' is the wordplay.
'idiot' becomes 'ass' (I've seen this before**).
'mature' becomes 'age' ('age' can be a synonym of 'mature').
'going round' indicates putting letters inside.
'university' becomes 'u'.
'ass'+'age'='assage'
'assage' going around 'u' is 'ASSUAGE'.
'in' acts as a link.
(Other definitions for assuage that I've seen before include "'Alleviate, appease (7)'" , "Appease, calm" , "Satisfy (a desire)" , "Make less severe, pain or hunger, say" , "'Make less severe, pain say (7)'" .)