if an excuse or an argument will not wash, people will not believe it or accept it.

That story about missing the last bus won't wash with me, young lady! (often + with)

• be caught with pants down
• be caught with trousers down
• be caught with your pants down
• be caught with your trousers down
• because of
• because of something
• be centre stage
• be chalk and cheese
• be champing at the bit
• be chasing tail
• be chasing your tail
• be chief cook and bottle washer
• be child's play
• be chilled to the bone
• be chilled to the marrow
• be chomping at the bit
• be climbing the walls
• be close to home
• be close to the bone
• be close to the mark
• be coining it
• be cold comfort
• be cold enough to freeze the balls off a brass monkey
• be coming apart at the seams
• be comme il faut