Insensible jazz fan needs a shot in the arm (9)
I believe the answer is:
catatonic
'insensible' is the definition.
(I've seen this before)
'jazz fan needs a shot in the arm' is the wordplay.
'jazz fan' becomes 'cat' (I've seen this before).
'needs' is a charade indicator (letters next to each other).
'shot in the arm' becomes 'tonic' (I've seen this before).
'cat'+'a'+'tonic'='CATATONIC'
(Other definitions for catatonic that I've seen before include "Insensible" , "In an immobile stupor" , "Having muscular rigidity and stupor" , "Unable to move" , "In a stupefied state" .)