if you want a simple clock, look up rltoday. This program can be included on the today screen and is a custom today item. You can do a ton of stuff with rltoday even if it is as simple as a small clock. Watch out though because you have to know how to use xml. If you have a good understanding of code you can always take the code others have written and edit it to fit how you want it to look. rltoday is also a very small memory print on your phone.
Link to website
If you need help programming a clock, I might be able to help but I am not that efficient with xml but have some knowledge.
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see attachment for sample image of my rltoday desktop