Attempt to conceal bad news in overwhelming defeat (9)
I believe the answer is:
whitewash
I believe this is a double definition.
'attempt to conceal bad news' is the first definition.
(I've seen this before)
'overwhelming defeat' is the second definition.
(I've seen this before)
'in' is the link.
(Other definitions for whitewash that I've seen before include "Cover-up -- wall coating" , "Gloss over faults with wall colouring?" , "Lime solution; cover up" , "Used on walls to cover up a misdemeanour?" , "Comprehensive defeat - type of paint" .)