Strongly criticise ending over no mafia deaths? Daft! (5)
I believe the answer is:
roast
'strongly criticise' is the definition.
(I've seen this before)
'ending over no mafia deaths? daft' is the wordplay.
'ending' indicates one should take the final letters.
The last letters of 'over no mafia deaths daft' are 'ROAST'.
(Other definitions for roast that I've seen before include "Get very warm" , "Cooked meat; criticise" , "Cook with dry heat" , "Trash" , "Swelter" .)