Like lady's protest in play that confounds sexes with vice (9)
I believe the answer is:
excessive
'like' is the definition.
Both the answer and definition are adjectives. Perhaps there's an association between them I don't understand?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for excessive that I've seen before include "Beyond normal limits" , "Over the top" , "Too much" , "More than is desirable" , "Inordinate, unreasonable" .)