University dissertation's about down-and-out (6)
I believe the answer is:
pauper
'down-and-out' is the definition.
(thesaurus)
'university dissertation's about' is the wordplay.
'university' becomes 'u' (abbreviation for university).
'dissertation' becomes 'paper' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'u' going within 'paper' is 'PAUPER'.
(Other definitions for pauper that I've seen before include "Extremely poor person" , "A very poor person, really broke" , "One with little money" , "Church mouse" , "Indigent type" .)