Meaning of TREAT in English
(VERY WELL) [noun] [U] [UK] [informal] - a treat very well; with good resultsIf you've spilt a drop of red wine on something and you don't want it to stain, put some salt on it - it works a treat.That soup was lovely - it went down a treat (= tasted very good)!I polished that old desk of grandma's and it came up a treat (= its appearance improved).
Cambridge English vocab. Кембриджский английский словарь. 2012