A can't find any command, or we do not have the option?

No such option. You have to right click on the clock and select 'Say the time' from the context menu that pops up.

This said, it would probably be a good option to add to those you already have as to what happens when you click on the clock. This way you could select 'Say the time' as that option and then assign an hotkey to the clock item like you can to any other items in the dock.

Ok, in v19.2 added 'Say the time' as a possible option to what happens when you click on the clock module.