Concealing a bad defeat (6)
I believe the answer is:
hiding
This clue could be a double definition.
'concealing a bad' is the first definition.
'hiding' can be an answer for 'concealing' ('hide' can be a synonym of 'conceal'). I am not certain of the 'a bad' bit.
'defeat' is the second definition.
(I have seen 'Severe defeat ' mean 'hiding' so perhaps 'defeat' could also mean 'hiding')
Can you help me to learn more?
(Other definitions for hiding that I've seen before include "Beating; severe defeat" , "Hushing up" , "Not publicising" , "Beating - retreat" , "physical punishment" .)