Possible Clues:

• What we're made of
• Substance, material
• No laughing ___
• Word that can follow the first parts of 17-, 25-, 42- and 55-Across
• Perhaps Busby and Queen are important
• Count carrying more weight after transitioning
• ''As a __ of fact . . .''
• Count gives mother in Rome a second heart
• 'What's the ___?'
• Issue before court might be regarded as comparatively dull