Cheers when husband quits and fails badly (5)
I believe the answer is:
tanks
'fails badly' is the definition.
(to tank is to fail terribly)
I cannot understand how the rest of the clue works.
(Other definitions for tanks that I've seen before include "Armed vehicles" , "Armored military vehicles" , "Bombs" , "Armoured military vehicles" , "Reservoirs - military vehicles" .)