University can upset single person (4)
I believe the answer is:
unit
'single person' is the definition.
(I've seen this in another clue)
'university can upset' is the wordplay.
'university' becomes 'U' (abbreviation for university).
'can' becomes 'tin' (both are metal containers).
'upset' says the letters should be written backwards.
'tin' backwards is 'nit'.
'u'+'nit'='UNIT'
(Other definitions for unit that I've seen before include "Subdivision of a whole" , "Constituent" , "Single person - group of people" , "Kitchen fitting" , "One - kitchen cabinet" .)