Depressed university teacher drinking whiskey (4)
I believe the answer is:
down
'depressed' is the definition.
(I know that depressed can be written as down)
'university teacher drinking whiskey' is the wordplay.
'university teacher' becomes 'don' (Oxbridge term for an academic).
'drinking' is an insertion indicator (inserted letters are consumed or drunk).
'whiskey' becomes 'W' (phonetic alphabet: alpha, bravo, charlie etc.).
'don' enclosing 'w' is 'DOWN'.
(Other definitions for down that I've seen before include "drink at speed" , "Blue" , "Not working (computer)" , "Feathers or hair" , "Some 13 Acrosses" .)