There is no ‘safe’ way to upgrade to a version newer than the one distributed, so your first priority should be to back up your system. If possible take an image of your SD card so you can get back to ‘now’ very quickly to try multiple ways if required.
Once you have a full back up, identify the version of libtorrent you need and whether it will work with your current version of deluge.
Then run sudo apt-get update && sudo apt-get dist-upgrade to ensure everything else is up-to-date and sudo apt-get install build-essentials so that you can build from source (you may need kernel headers too).
Download the source code for the version of libtorrent (and deluge if needed) you require and follow the directions in their readme files to build and install them.
Please note though if this causes problems elsewhere you are likely to be asked to revert these changes before anyone can offer you support.