No, that's not what iCloud is for, and in actuality, it would be prudent to leave your data on your external hard drive than to trust it in the cloud that's hosted by a company. In other words, you never know the day the company decides to pull the plug on this service though I don't think Apple will do something like that. Or who knows the day you cannot access your data because the servers are down indefinitely.
Besides, iCloud is not as robust as your third-party cloud based options, e.g. OneDrive, Dropbox, Google Drive/Photos, etc. iCloud is a syncing service that basically syncs your data across all of your devices, making it easily accessible to you.