In a small saucepan, heat port over medium-high heat until hot. Remove from heat, add cherries, and cover; let stand 15 minutes.
Heat olive oil in a medium skillet over medium-high heat. Add shallots and cook, stirring, until translucent, 2 to 3 minutes. Add rhubarb and cook, stirring, 3 to 4 minutes. Transfer mixture to a large bowl; set aside.
Add cherry-port mixture to skillet and let simmer for 1 minute. Add chicken stock, thyme, pepper, salt, and cloves; simmer until reduced by one-third. Whisk in butter, a few cubes at a time, making sure each addition is fully incorporated before adding the next. Return rhubarb mixture to skillet and let simmer for 1 minute. Serve immediately.