Boozy yob, exceptionally large, joining group outside university (5,4)
I believe the answer is:
lager lout
'boozy yob' is the definition.
(I've seen this before)
'exceptionally large joining group outside university' is the wordplay.
'exceptionally' is an anagram indicator.
'joining' means one lot of letters goes inside another (inserted letters join the word).
'group' becomes 'lot' ().
'outside' means one lot of letters goes inside another (some letters go outside others).
'university' becomes 'U' (abbreviation for university).
'large' anagrammed gives 'agerl'.
'lot' enclosing 'u' is 'lout'.
'agerl' placed into 'lout' is 'LAGER LOUT'.
(Other definitions for lager lout that I've seen before include "Drinker behaving antisocially" , "menace" , "Alcohol-fuelled youth" , "Troublesome drunk" , "Aggressive young drunk" .)