Drug work by one university member (5)
I believe the answer is:
opium
'drug' is the definition.
(I know that opium is a depressant)
'work by one university member' is the wordplay.
'work' becomes 'op' (common abbreviation for 'opus').
'by' is a charade indicator (letters next to each other).
'one' becomes 'i' (Roman numeral).
'university' becomes 'u' (abbreviation for university).
'member' becomes 'm' (political abbreviation).
'op'+'i'+'u'+'m'='OPIUM'
(Other definitions for opium that I've seen before include "wars with China" , "Duller" , "powerful drug" , "Dried juice of white poppy" , "De Quincey confessed to eating it" .)