Sorry for the delay in responding, but have had trouble logging in (password??). Anyway, it occured to me that the icon isn't a circle with an L in it, but an alarm clock.
To the best of my knowledge I don't have any apps with alarms set, and have never seen this icon before. I've checked CALENDAR and CLOCK and didn't find anything.
(I took a screenshot, but I don't know how to include it as an attachment to my reply. Didn't see a paperclip icon or attachment option.)