Man I arranged to host first of London University’s ex-students (6)
I believe the answer is:
alumni
'ex-students' is the definition.
(I've seen this before)
'man i arranged to host first of london university's' is the wordplay.
'arranged' is an anagram indicator.
'to host' indicates putting letters inside.
'first of' indicates taking the first letters.
The initial letters of 'london universitys' is 'lu'.
'man'+'i'='mani'
'mani' is an anagram of 'amni'.
'amni' going around 'lu' is 'ALUMNI'.
(Other definitions for alumni that I've seen before include "Past pupils, former students" , "Ex-students" , "Graduates of an institution" , "Graduates of a college" , "Former (college) students" .)