Taboo violated by duke. What a pity! (3,3)

I believe the answer is:

too bad

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(Other definitions for too bad that I've seen before include "Tough" , "That's regrettable, informally" , "regrettably" , "Informally regrettable, a pity" , "Informally regrettable - excessively wicked" .)

I've seen this clue in The Hindu.

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