I use an Exchange server for work email and calendar, and I use an iCloud/iCal calendar at home and freelance business.
I want to sync all my iCloud calendar items - not contacts, email or anything else.
How can I do this?
The two services are not designed to easily merge with one another. There are numerous syncing tools available, but when you have multiple sync services interacting with each other (in this case: iCloud, middle man service & Exchange are each their own sync service) you dramatically increase the chance of serious sync corruptions.
As your goal is to see all of your calendars everywhere, I recommend setting up both services on all of your devices. You will want to use the following apps, depending on platform, for an ideal experience and visibility to both calendars:
Mac: use Apple Calendar (formerly, iCal). See this guide for setting up both account types.
It may be possible for you to sync the two calendars but its a bit of a convoluted process.
Don't know how effective this is but it may be your best option.
(iCloud will apparently sync with a standalone version of outlook out of the box)