Related Clues:

• Gets comfortable
• Rooms for contemplative leisure, perhaps
• Wasps' homes
• Places to roost
• Places to brood
• Places to put your feet up
• Places for 56-Across
• Some are lined with books
• Reading rooms
• Fits one inside the other
• Homes in trees
• Embeds
• Branch houses
• Squirrels' constructions
• Bird houses?