In serious outbreak criticise bungling medic (8)
I believe the answer is:
pandemic
'in serious outbreak' is the definition.
'pandemic' can be an answer for 'outbreak' (pandemic is a kind of outbreak). I am not certain of the 'in serious' bit.
'criticise bungling medic' is the wordplay.
'criticise' becomes 'pan' (informal term meaning to criticise heavily).
'bungling' is an anagram indicator (I've seen this in other clues).
'medic' anagrammed gives 'demic'.
'pan'+'demic'='PANDEMIC'
(Other definitions for pandemic that I've seen before include "Global disease" , "extensive disease" , "Widespread health problem" , "(Of a disease) affecting a wide area" , "Occurring throughout the world, perhaps disease" .)