Am alert; am wandering in a former college (4,5)
I believe the answer is:
alma mater
'a former college' is the definition.
(I've seen this before)
'am alert am wandering' is the wordplay.
'wandering' indicates an anagram.
'am'+'alert'+'am'='amalertam'
'amalertam' is an anagram of 'ALMA MATER'.
'in' is the link.
(Other definitions for alma mater that I've seen before include "College one attended" , "One's place of education" , "College from which one has graduated" , "originally taught here?" , "Alert mama to the old school" .)