Possible Clues:

• Timepiece with a gnomon
• Outdoor time-telling device
• Fair-weather timepiece
• On a fine day, time for reading here in the garden?
• I land us in trouble getting something for the garden perhaps
• Horological device
• Shadow clock
• Timepiece put back post-daylight
• Put a group of students up in an erection in the garden?
• No hands for a time