drop a clanger make an embarrassing or foolish mistake. British informal
☞ Dropping something that makes a loud clang attracts attention; this mid-20th-century expression is used especially in the context of a very embarrrassing or tactless act or remark made in a social situation.
2003Jozef ImrichA Media Dragon I don't live my life in a simplistic way. Sometimes I drop a clanger, sometimes I make a mistake, other times I get it right