Butcher's ware? What nonsense! (5)
I believe the answer is:
tripe
'nonsense' is the definition.
(informal term for nonsense or false information)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for tripe that I've seen before include "Edible lining of cow's stomach - rubbish" , "Rubbish, nonsense" , "which a freegan might eat?" , "Ruminant's stomach lining" , "Rubbish (colloq.)" .)