They're square sundials for example (3-6)
I believe the answer is:
old-timers
'sundials for example' is the definition.
I can't judge whether this definition defines the answer.
'they're square' is the wordplay.
'they're' becomes 'oldtimer' (I can't explain this - if you can you should believe this answer much more).
'square' becomes 's' (abbreviation).
'oldtimer'+'s'='OLD-TIMERS'
Can you help me to learn more?
(Another definition for old-timers that I've seen is " People with long experience, like ancient watches".)