Gloomy academic, exhausted, drinking whiskey (8)
I believe the answer is:
downbeat
'gloomy' is the definition.
(I've seen this before)
'academic exhausted drinking whiskey' is the wordplay.
'academic' becomes 'don' (type of academic - especially at Oxbridge).
'exhausted' becomes 'beat' (I've seen this in another clue).
'drinking' is an insertion indicator (inserted letters are consumed or drunk).
'whiskey' becomes 'W' (phonetic alphabet: alpha, bravo, charlie etc.).
'don'+'beat'='donbeat'
'donbeat' placed around 'w' is 'DOWNBEAT'.
(Other definitions for downbeat that I've seen before include "Dismal and depressing" , "Casual" , "Depressed - relaxed" , "Gloomy; laid-back" , "gesture by conductor" .)