Possible Clues:

• Stashed
• Part of orchid denied or concealed
• Like some assets and agendas
• Leather cut to go over shelter that's secret
• With 68-Across, ulterior motive ... or what 21-, 37- and 59-Across each has?
• Art to be found in certain puzzles — and in the other across solutions
• Covert
• In high definition, I study the unknown
• Feature of Copenhagen — Danish design kept secret
• Secret greeting before daughter is taken into private room