Yobs, many hanging around university (5)
I believe the answer is:
louts
'yobs' is the definition.
(I've seen this before)
'many hanging around university' is the wordplay.
'many' becomes 'lots' (I've seen this before**).
'hanging around' indicates putting letters inside.
'university' becomes 'u'.
'lots' enclosing 'u' is 'LOUTS'.
(Other definitions for louts that I've seen before include "Coarse types" , "Yobs" , "Uncouth aggressive men" , "Dolts" .)