Discredit Madeleine dismissing lie (6)
I believe the answer is:
demean
'discredit' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for demean that I've seen before include "Lower in dignity or respect" , "Lower in dignity or reputation" , "Belittle; degrade" , "Lower in status or reputation" , "Cause to lose respect" .)